Method and system for information transfer and replication between spatially distinct points via engineered quantum states

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a system and method for communication, and more particularly to a system and method for transferring and replicating information between spatially distinct points using engineered quantum states.

2. Description of the Related Art

Efficient and reliable transfer of information is crucial to the preservation of knowledge and the advancement of progress. Contemporary computers, which play an invaluable role in this area, are capable of increasingly rapid information processing primarily through the downscaling of their constituent integrated circuitry. This well-defined evolutionary process has engendered phenomenal progress in information technology during the last few decades. However, the current trend of shrinking conventional semiconductor-based technology cannot continue indefinitely.

At the heart of present-day electronics are semiconductor devices which, although microscopic, nonetheless operate by controlling the flow of electrical currents along circuit paths defined by wires and other conducting areas. In one analogy, electrons are essentially shoved into one end of a conducting interconnection and emerge from another end like water in a garden hose. Conventional electronic devices are much larger than the wavelengths of the electrons comprising the currents steered through them, so quantum effects are generally ignored. However, because present scaling trends will soon demand device sizes that approach the electron wavelength limit, the full wave nature of electrons must be considered and will play an increasingly vital role in device operation and performance.

Therefore, given this view of the inherent limitations on conventional semiconductor-based electronics, new systems and methods for information transfer that rely on, rather than ignore, the quantum nature of electrons are critically needed.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system and method for transferring information between spatially distinct points without requiring the usual wiring and current transfer of conventional electronics.

It is a further object of the present invention to provide structures fabricated on a sufficiently small length scale (on the order of the electron Fermi wavelength) to enable the engineering of confined quantum states as desired.

It is a further object of the present invention to modulate these quantum states, for example by perturbing the electronic potential at a particular location, thereby encoding information into the quantum states. If the modulation frequency is lower than the frequency corresponding to the damping time of the structures, the quantum states may be modulated adiabatically, thus enabling information transmission without power dissipation.

It is a further object of the present invention to couple the perturbation (or a localized quantum response thereto) with quantum states guided throughout the structure. The invention then selects and focuses the distributed quantum states for detection at a location spatially distinct from the modulation point. The detection of the modulating information is performed specifically through the wave nature of the quantum states, versus mere electrical current flow as with existing devices. The information transferred is not limited to a given format, i.e. it may be analog, digital, or any combination thereof.

It is a further object of the present invention to exploit the orthogonality of quantum wavefunctions to enable multiple channels of information to be transferred simultaneously through the same volume of space without crosstalk. Further, information may be transferred in either direction, that is, both to and from both the modulation point and the detection point, simultaneously, as there is no inherent directionality to a quantum state.

It is a further object of the present invention to provide structures enabling logic functions and memory operations to be performed on the transmitted information.

The structure is preferably a resonator designed to have two antinodes, which are spatial locations where the electron density distribution is relatively large. If a transmitter (which is anything that affects a modulation in a quantum state) is placed at a first antinode and a receiver (which is anything sensitive to a modulated aspect of a quantum state) is placed at a second antinode, information transfer between the transmitter and receiver is optimized because the modulation affected at the receiver by the transmitter is maximized. Conversely, a transmitter located at a node (spatial location where a quantum state's density distribution is zero) will have minimal ability to modulate a quantum state and therefore minimal ability to transmit a signal to a receiver. Similarly, a receiver placed at a node of a quantum state will detect very little modulation of the quantum state and hence have minimal ability to receive a signal.

Alternately, structures may be designed with more than one transmitter and more than one receiver. Changes to the physical structure of the resonator may also modulate the quantum states available for information transmission. Furthermore, the quantum states used for communication need not even be occupied to be modulated.

In the preferred embodiment of the present invention, the structure for communicating information is an elliptically-shaped quantum corral assembled from cobalt atoms on a conductive copper substrate. The transmitter is preferably a cobalt atom positioned at the first focus of the ellipse. The receiver is preferably a scanning tunneling microscope (STM) tip positioned above the second focus of the ellipse. The geometric properties of the ellipse project the particular quantum mechanical signature (e.g. Kondo resonance) of the cobalt atom at the first focus onto the second, empty focus. In effect, a phantom image or “mirage” of the real cobalt atom appears at the receiver at the second focus and influences the receiver in a manner very similar to what would result from a cobalt atom actually existing at the receiver. In this case, the receiver detects a strong dip in tunneling conductance at the second focus, indicating the presence of the cobalt atom at the first focus. An electron reservoir is usually necessary to allow the invention to be operated more than once.

The invention is not limited to this structure or modulation method, however. Theoretically, a single atom could serve as the transferring structure because its electrons are confined to quantum states that could be modulated on one side of the atom and detected on the other side of the atom, or on the other side of the universe. In that case, quantum states are engineered by selecting a particular atom and the specific energy levels to be modulated.

The present invention thus provides a unique and nonobvious structure and method which overcome the limitations of conventional microelectronics, and embody a new paradigm for information transfer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a schematic diagram of a communication system using a quantum state to transfer information between a transmitter and a receiver according to a preferred embodiment of the present invention;

FIG. 2

is a schematic diagram of an ellipse;

FIG. 3

is a topographic scanning tunneling microscope (STM) image of an elliptical quantum corral resonator according to a preferred embodiment of the present invention;

FIG. 4

is a schematic diagram of the eigenmodes of the elliptical quantum corral resonator according to a preferred embodiment of the present invention;

FIGS. 5A and 5B

are plots of STM tip height depicting transmission of digital information between the foci of the elliptical quantum corral resonator using an atom placed at a focus (

5

A) and away from a focus (

5

B);

FIG. 6

is a topographic STM image of the elliptical quantum corral resonator having an atom placed at a focus corresponding to

FIG. 5A

according to a preferred embodiment of the present invention;

FIG. 7

is a conductivity image of the empty elliptical quantum corral resonator according to a preferred embodiment of the present invention.

FIG. 8

is a conductivity image of the elliptical quantum corral resonator having an atom placed at a focus corresponding to FIG.

5

A and

FIG. 6

according to a preferred embodiment of the present invention;

FIG. 9

is a topographic STM image of the elliptical quantum corral resonator having an atom placed away from a focus;

FIG. 10

is a conductivity image of the elliptical quantum corral resonator having an atom placed away from a focus corresponding to

FIG. 8

;

FIG. 11

is a conductivity difference plot of the elliptical quantum corral resonator illustrating the transmission of analog information encoded in the spectral signature of a cobalt atom according to a preferred embodiment of the present invention;

FIGS. 12A and 12B

are plots of conductivity of the elliptical quantum corral resonator versus sample bias voltage according to a preferred embodiment of the present invention;

FIG. 13

is a topographic STM image of a circular quantum corral resonator according to a second embodiment of the invention;

FIGS. 14A and 14B

are schematic diagrams of the eigenmodes of the circular quantum corral resonator according to the second embodiment of the present invention;

FIG. 15

is an STM image of cross-channel communication using orthogonal eigenmodes of the circular quantum corral resonator according to the second embodiment of the present invention;

FIG. 16

is an STM image of cross-channel communication using orthogonal eigenmodes of the circular quantum corral resonator according to the second embodiment of the present invention;

FIG. 17

is a schematic diagram of a pair of interdigitated elliptical quantum corral resonators simultaneously communicating information through two independent channels in the same region of space according to an alternate embodiment of the present invention;

FIG. 18

is a schematic diagram of a pair of interconnected elliptical quantum corral resonators sharing a common focus according to a third embodiment of the present invention; and

FIG. 19

is a schematic diagram of a pair of parabolic electron reflectors forming a communication system according to a fourth embodiment of the present invention.

Like numbers indicate like parts throughout the several views.

DETAILED DESCRIPTION

An electronic quantum state may be extended in space. Its energy and probability distribution are uniquely determined by the global potential that it samples. A local change in potential at one point can alter or perturb the quantum state in a measurable way. Generally, if the quantum wavefunction is extended over distances larger than the size of the local change in potential, this perturbation can be detected at a remote location where the probability distribution of the quantum state is sufficiently large. At this new location, the original change in potential could be directly undetectable, but may be indirectly determined by querying the extended quantum wavefunction that samples both locations simultaneously.

Referring now to

FIG. 1

, a schematic diagram is shown of a communication system using a quantum state to transfer information between two or more spatially distinct points according to a preferred embodiment of the present invention. System

100

does not require the usual wiring and current transfer of conventional electronics; rather, the system of the present invention utilizes the quantum wave nature of electrons per se for transmission and reception of information.

In the present invention, information to be transferred begins its journey at transmitter

102

, which may be any physical entity that locally affects a modulation in a quantum state

104

. For example, transmitter

102

may perturb the electronic potential at a particular point in space, thereby encoding information by modulating quantum state

104

. Alternately, transmitter

102

may affect the density distribution, spin (magnetic moment), or occupancy of quantum state

104

. Transmitter

102

is thus coupled to quantum state

104

(or a localized quantum response to the modulation of quantum state

104

) which is distributed throughout system

100

. A modulation of quantum state

104

will generally be manifest throughout the volume of space in which quantum state

104

exists both before and after the modulation caused by transmitter

102

. Quantum state

104

may be thought of as the “medium” carrying the information.

System

100

then selects and focuses modulated quantum state

104

for detection at a location spatially distinct from the modulation point. Receiver

106

may be any physical entity which is locally sensitive to some aspect of quantum state

104

. For purposes of the present invention, by “locally” it is meant that transmitter

102

does not directly influence receiver

106

but instead influences quantum state

104

. Receiver

106

detects the modulation originally affected by transmitter

102

and outputs the information transferred. Transmitter

102

and receiver

106

are thus operatively coupled together via quantum state

104

even though spatially separated. The present invention is not limited to any specific format of information being transferred, i.e. it may be analog, digital, or any combination thereof. A preferred embodiment of the invention uses a two-point geometry that allows for one source and one destination, but the geometry may be extended to multiple source and destination locations.

There are many known methods and means to create potentials, typically in a solid or on the surface of a solid, which result in a quantum state

104

for one or more electrons. For example, the core electron states of the atoms that compose a solid are a set of quantum states

104

. Another example is the set of quantum states

104

of electrons in a semiconductor heterostructure which are first confined to a two-dimensional layer due to the layering of the heterostructure, and then further confined to discrete states by suitably designed electrodes in the heterostructure. Further examples are the quantum states

104

of a molecule and the quantum states

104

of a quantum dot.

Another example of a structure for producing specific quantum states

104

is a “quantum corral”, as known conventionally, which is an arrangement of atoms or molecules designed to substantially confine electrons. Quantum corrals are built on the surface of certain materials which, due to the inherent electronic nature of the material and surface characteristics, have electrons which form a two-dimensional electron gas on the surface of the materials. These electrons may be further confined by creating an electron scattering potential which limits these electrons in the plane of the surface. The scattering potential may be produced by atoms on the surface, step edges, defects, and by other means readily apparent to those skilled in the art. Further, the invention is not limited to two-dimensional structures.

Referring now to

FIG. 2

, a schematic diagram of an ellipse

200

is shown. Ellipse

200

is a locus of points P wherein the sum of the distance of each point P from two fixed points F

1

and F

2

is a constant. The two fixed points of ellipse

200

are a left focus

202

and a right focus

204

. Ellipse

200

may be described by an eccentricity e and a semimajor length a.

Referring now to

FIG. 3

, a topographic STM image of an elliptical quantum corral or resonator

300

according to a preferred embodiment of the present invention is shown. Resonator

300

is fabricated on a sufficiently small length scale (on the order of the electron Fermi wavelength) to enable the engineering of quantum states

104

as desired. An STM preferably positions atoms

302

to form the walls of resonator

300

in the shape of ellipse

200

; alternately, molecules or etched surfaces may form the walls. In an exemplary implementation of the invention, resonator

300

includes 36 individual cobalt atoms

302

positioned on the [111] surface of a copper substrate. Resonator

300

of

FIG. 3

has an eccentricity of 0.5 and a semimajor axis of 71.3 Angstroms (Å). The size and shape of resonator

300

are specifically designed to result in quantum states

104

near the Fermi level of the underlying copper having two antinodes (spatial locations at which the distribution density is high). Resonator

300

harbors approximately 100 resonating electrons.

The bulk conduction electrons and the electrons in the surface states of the conductive copper substrate serve as an electron reservoir

304

. An electron reservoir

304

is usually necessary to allow the invention to be operable more than once. Quantum state

104

should be weakly coupled to electron reservoir

304

in order to, for example, re-establish the occupancy of quantum state

104

by either filling or emptying quantum state

104

after quantum state

104

is read out by receiver

106

. The coupling to electron reservoir

304

should not be strong enough to destroy the conditions which give rise to a discrete set of quantum states

104

. Electron reservoirs

304

may also be tunnel barriers which leak electrons into quantum states

104

in semiconductor heterostructures. Transmitters

102

and receivers

106

may also serve as electron reservoirs

304

. For certain conditions, electrons occupying other quantum states

104

of resonator

300

could serve as electron reservoir

304

, especially if they are themselves connected to an electron reservoir

304

. If the modulation frequency of quantum states

104

is lower than the frequency corresponding to the damping time of resonator

300

, quantum states

104

may be modulated adiabatically, thus enabling information transmission without power dissipation. Some minimal power dissipation may be required for reception, however.

Receiver

106

may be designed to utilize the exclusion principle to characterize quantum state

104

. Such a receiver

106

would attempt to impose a spin or energy transition upon quantum state

104

; if such a transition occurs, that would signify for example a logic “1”, otherwise the exclusion principle would not allow such a transition to occur, signifying a logic “0”. In this way, no electron reservoir

304

would be required.

Transmitter

102

may be formed, for example, by a suitably patterned electrode on a semiconductor heterostructure, by an atom or group of atoms placed on the boundary, interior, or exterior of a quantum corral which affects quantum state

104

of the corral, by an electrode for applying an electric field, by a local magnetic field, or by an atom with a spin or magnetic moment. There may be one or more transmitters

102

per quantum state

104

, and there may be one or more quantum states

104

per transmitter

102

.

Receiver

106

may be a tunnel barrier or local lowering of the confining potential through which an electron may move while transitioning out of quantum state

104

, or an atom or group of atoms which undergo an identifiable change due to an alteration in quantum state

104

in the vicinity of the atom or group of atoms, or any means for locally probing quantum state

104

such as the tip of an STM. As with transmitters

102

, there may be one or more receivers

106

per quantum state

104

, and there may be one or more quantum states

104

per receiver

106

. Receiver

106

may even be the same physical entity or part of transmitter

102

.

Referring now to

FIG. 4

, a schematic diagram of the eigenmodes of resonator

300

of

FIG. 3

is shown, according to a preferred embodiment of the present invention. These eigenmodes may be calculated using a hard-wall box approximation for resonator

300

. The particular size and shape of resonator

300

produces distinct probability density amplitude peaks

400

and

402

at or near the Fermi energy E

F

(V=0) to resonate confined electrons. These probability peaks are very near the classical foci (

202

and

204

) of ellipse

200

, and are important for the information transfer example described below.

Information is preferably propagated by system

100

in a specific region of space using a quantum state

104

having a probability distribution that is peaked in two or more distinct points that are spatially well-separated from each other. Quantum state

104

may be modulated only at places where the wavefunction is nonzero, and the extent of the modulation depends largely upon the magnitude of the state density at the modulation point. For example, a negative electrical potential may be applied at a location corresponding to peak

400

in the density distribution of quantum state

104

(corresponding to left focus

202

in FIG.

2

). The density distribution at left focus

202

is thereby reduced, hence modulating quantum state

104

. The effect of such an applied potential is large wherever the density distribution is large, such as at peaks

400

and

402

.

Generally, therefore, placement of a transmitter

102

at one such peak results in a large modulation of quantum state

104

. Placement of a receiver

106

at another such peak results in a large signal being detected by receiver

106

. Thus, information transfer between transmitter

102

and receiver

106

is optimized because the modulation affected at receiver

106

by transmitter

102

is maximized. Similarly, noise sources located at nodes (spatial locations where the density distribution is zero) will have minimal influence on the communication between transmitter

102

and receiver

106

because quantum state

104

cannot be modulated at a node.

Referring now to

FIGS. 5A and 5B

, plots of STM tip height versus distance along the major axis of resonator

300

are shown as examples of digital information transfer. The information source is at left focus

202

(dotted vertical line in

FIG. 5A

) and the information destination is at right focus

204

(dotted vertical line in FIG.

5

B).

Transmitter

102

is implemented in the preferred embodiment of the present invention by placing a cobalt atom on the substrate surface of resonator

300

at its left focus

202

. An STM tip positioned directly over transmitter

102

will typically be 0.8 Å above the substrate to maintain the constant current value used in the experiment, versus the 0.2 Å STM tip height typically needed to maintain the same constant current value when there is no transmitter

102

present.

The scattering of surface state electrons at left focus

202

creates a node in quantum state

104

at left focus

202

. Quantum state

104

is significantly perturbed by placing a node-creating atom at what would otherwise be an antinode in quantum state

104

. This perturbation is apparent wherever the density distribution is large, i.e. at antinodes of quantum state

104

.

An exemplary receiver

106

is implemented by placing an STM tip over right focus

204

of resonator

300

. The presence of the atom at left focus

202

may be detected by measuring the density of quantum state

104

at right focus

204

. The STM tip height above the substrate at right focus

204

required to maintain a constant current value varies with the density of quantum state

104

at right focus

204

. When an atom is positioned at left focus

202

, it repels electrons and thus lowers the density distribution at right focus

202

. The STM tip over right focus

202

must therefore be lowered closer to the substrate to maintain the constant current value.

Changes in the STM tip heights required to maintain a constant current value as shown in

FIGS. 5A and 5B

may represent changes in logic values due to perturbation of quantum state

104

. The first logic state (“0” or “1”)

500

at left focus

202

is detected by the tip height value at right focus

204

and determines the second logic state

502

at right focus

204

. Logic “0” states (e.g., dashed lines) correspond to no atom existing at left focus

202

, and logic “1” states (e.g., solid lines) correspond an atom existing at left focus

202

. In other words, right focus

204

of resonator

300

is empty in this example, but when probed it reveals the state of left focus

202

of resonator

300

. Such information transfer by quantum state

104

modulation does not require intricate interconnection wiring as with conventional electronics. Scaling can therefore proceed downward to atomic dimensions.

Further, the information transferred is not restricted to binary values, e.g. the two tip specific STM height states

500

and

502

shown in

FIGS. 5A and 5B

. The position of the atom at left focus

202

maps a range of input values to a range of output values at right focus

204

. This corresponds to and enables a multi-state digital information transfer. Additionally, the local potential at left focus

202

may be modulated continuously (e.g., by changing the voltage on a gate), in which case the information transferred will be analog. Thus, the present invention allows for both digital and analog information transfer depending upon the local potential placed on one of the resonator

300

foci. Additionally, the presence or absence of an atom at a focus of resonator

300

may serve as a one bit memory function. Further details of the experimental implementation of this aspect of the present invention are described by the next several figures, and in a journal article scheduled for publication in

Nature

on Feb. 3, 2000 (volume 403, pages 512-515) and included as an Appendix and incorporated herein by reference.

Referring now to

FIG. 6

, a topographic STM image of resonator

300

having a cobalt atom

600

at left focus

202

is shown, according to the preferred embodiment of the present invention. Cobalt atoms

600

on the [111] copper surface exhibit the Kondo effect, which is a many-body resonance occurring when conduction electrons align their spins to screen the localized magnetic moment of cobalt atom

600

. The Kondo resonance of cobalt atom

600

may be used to impress a unique spectroscopic signature upon quantum state

104

, with that signature then being detected elsewhere by measuring the energy dependence of the density of quantum state

104

at the remote location. The invention is not limited to the use of cobalt atoms, or other atoms exhibiting the Kondo effect; however, the Kondo effect results in a sharp suppression in differential conductivity dI/dV of particular utility.

Referring now to

FIG. 7

, a conductivity image of empty resonator

300

is shown, according to a preferred embodiment of the present invention.

Referring now to

FIG. 8

, a conductivity image of resonator

300

having a cobalt atom

600

placed at left focus

202

corresponding to

FIG. 6

is shown, according to a preferred embodiment of the present invention. The background image of empty resonator

300

from

FIG. 7

has been subtracted away to more clearly depict the influence of transmitter

102

(atom

600

at left focus

202

) on conductivity. Transmitter

102

produces a strong dip in tunneling conductance dI/dV as a function of sample bias V, centered around the Fermi energy of the copper substrate (V=0). The Kondo resonance may thus be detected spectroscopically by measuring the differential conductance dI/dV close to the Fermi energy. Conductance images may be taken simultaneously with topographic images by applying a small ac modulation voltage to the dc bias, in order to obtain a spatial map of the Kondo spectral signature.

The Kondo signature is shown by the bright regions

800

and

802

in the image of

FIG. 8. A

large Kondo resonance

800

is spatially centered on transmitter

102

at left focus

202

of resonator

300

and dissipates over a lateral length scale of about 10 Å. A smaller Kondo resonance

802

is spatially centered on right focus

204

of resonator

300

. The invention therefore uses the strong and distinct spectroscopic features of the Kondo effect as an “image source” and uses the geometric properties of ellipse

200

to project the spectroscopic Kondo signature of transmitter

102

at one focus (

202

) onto the opposite, empty focus (

204

). In effect, a phantom image or “mirage” of real cobalt atom

600

has been projected across resonator

300

and appears as smaller Kondo resonance

802

. The invention produces a faithful spectroscopic replica (e.g., a “virtual atom”) of the real cobalt atom

600

at the opposite focus (

204

) such that the resonance widths (e.g., implied Kondo temperatures) are equivalent. The present invention thus allows remote probing of cobalt atom

600

by measuring its spatially separated spectroscopic mirage or virtual replica.

Referring now to

FIG. 9

, a topographic STM image of resonator

300

having a cobalt atom

900

placed away from left focus

202

is shown.

Referring now to

FIG. 10

, a conductivity plot of resonator

300

having a cobalt atom

900

placed away from left focus

202

corresponding to

FIG. 9

is shown. The background image of empty resonator

300

from

FIG. 7

has again been subtracted away to more clearly depict the influence of cobalt atom

900

on conductivity. From this image, it is clear that because cobalt atom

900

is placed away from either of the foci (

202

and

204

), no image replica of cobalt atom

900

will be projected across resonator

300

. Only the Kondo signature of cobalt atom

900

itself is apparent as bright spot

1000

.

To recap,

FIGS. 5 through 9

illustrate an embodiment combining analog and digital information transfer within a resonator. In each instance, a cobalt atom is placed inside the resonator, a simultaneous constant-current topograph and dI/dV map are acquired, and the background dI/dV map (

FIG. 7

) is subtracted to obtain dI/dV difference images (

FIGS. 8 and 10

) showing the sensitivity to the Kondo resonance.

FIGS. 6 and 8

illustrate that when a cobalt atom is placed at a focus of the ellipse, a Kondo resonance appears both at the occupied focus and at the empty focus. The resonator couples the two foci in a manner permitting transmission of the spectral information at the occupied focus (the transmitter) to the empty focus (the receiver). Thus, the spectral signature can be viewed as analog information being transferred between the two foci. In addition, the transmission may be digitally modulated by moving the cobalt atom off focus. This condition is illustrated in

FIGS. 9 and 10

, in which only the Kondo resonance at the transmitter appears. This modulation may also be implemented by modifying the magnetic characteristics of the transmitter atom. For example, a second cobalt atom may be bound to the transmitter atom to form a nonmagnetic dimer, in which case the Kondo signature at the destination focus is also extinguished.

Referring now to

FIG. 11

, a plot of resonator

300

conductivity difference, illustrating the transmission of analog information encoded in the spectral signature of cobalt atom

600

is shown, according to a preferred embodiment of the present invention.

FIG. 11

is a perspective plot derived from

FIG. 8

data. The quality of interfocus transmission is depicted; the signal from the destination “phantom” atom (receiver

106

) at right focus

204

is roughly one-third the magnitude of the signal arising from the “real” source atom

600

(transmitter

102

) at left focus

202

. The fidelity of the transfer can be further examined by comparing the spectra obtained over the occupied left focus

202

and the empty right focus

204

.

Referring now to

FIGS. 12A and 12B

, plots of resonator

300

conductivity versus sample bias voltage are shown, according to a preferred embodiment of the present invention. In this case, conductivity is measured by the STM in open-loop mode. The signal detected at receiver

106

is highly correlated with the signal from transmitter

102

, as shown by very similar line widths, line shapes, and zero-bias offsets (solid lines). Further, the detected signal is confined to a region of space of comparable length scale to the source signal, as shown by comparison of data taken on the foci (

202

and

204

) versus data taken 5 Å off the foci (dashed lines) which show a considerably weakened Kondo resonance.

Referring now to

FIG. 13

, a topographic STM image of a circular quantum corral resonator

1300

is shown according to a second embodiment of the invention. Instead of an elliptically-shaped corral as used in the preferred embodiment, the second embodiment uses circular resonator

1300

to define two spatially overlapping quantum states

1400

and

1402

. A key advantage of the second embodiment becomes evident by considering the two degenerate orthogonal quantum states

1400

and

1402

of resonator

1300

, each having an angular momentum quantum number of 1.

Referring now to

FIGS. 14A and 14B

, schematic diagrams of the eigenmodes of resonator

1300

are shown, according to the second embodiment of the present invention. Resonator

1300

has a radius of 63.5 Å in this embodiment. The quantum states

1400

and

1402

depicted both correspond to one unit of angular momentum (e.g.,

1

=1.0), and are each peaked in two places near the center of resonator

1300

. Resonator

1300

may be viewed as a very low eccentricity ellipse

200

, with foci close to its center.

Normally, due to the rotational symmetry of circular resonator

1300

, such quantum states

1400

and

1402

will appear as concentric rings when a probability distribution is measured. However, the symmetry may be broken intentionally to “lock in” a particular orientation of the pair of quantum states

1400

and

1402

. In this case, a first cobalt atom

1404

(not shown) serving as a transmitter

102

is placed off center at a radial distance corresponding to the peaks in the

1

=1 quantum state

1400

to break the rotational symmetry, as depicted in FIG.

14

A. Calculated magnitudes of the resulting quantum states

1400

and

1402

present near the Fermi energy of resonator

1300

are shown in

FIGS. 14A and 14B

.

The orthogonal quantum state

1402

shown in

FIG. 14B

thus now has lobes rotated ninety degrees with respect to quantum state

1400

shown in FIG.

14

A. One wavefunction's nodes are thus located at the other wavefunction's antinodes. The quantum state

1402

shown in

FIG. 14B

may be used for a separate and distinct information transfer channel because the quantum states

1400

and

1402

depicted in

FIGS. 14A and 14B

will always remain orthogonal to each other. Transmitter

102

is located at a position corresponding to an antinode in quantum state

1400

of the channel over which it is intended to transmit information.

Referring now to

FIG. 15

, a rendered STM image of single-channel communication using quantum state

1400

of resonator

1300

is shown according to the second embodiment of the present invention.

FIG. 15

is created from data gathered according to the differential conductivity methods described with respect to

FIGS. 5 through 10

above. The cobalt atom

1404

serving as transmitter

102

projects its Kondo signature to the opposing

1

=1 eigenstate lobe or “focus”, hence the geometry depicted in

FIG. 14A

may be used for information transfer as described in the preferred embodiment. A receiver

106

should be placed at the antinode of quantum state

1400

being altered by cobalt atom

1404

for optimum information transfer.

Referring now to

FIG. 16

, a rendered STM image of dual-channel communication using orthogonal quantum states

1400

and

1402

of resonator

1300

is shown according to the second embodiment of the present invention. A second cobalt atom

1406

(not shown) serving as a second transmitter

1500

is placed an identical distance away from the center of resonator

1300

but at a position ninety degrees away from the location of the first cobalt atom

1404

. Second transmitter

1500

projects its Kondo signature to its own opposing “focus” depicted in FIG.

14

B.

In other words, second transmitter

1500

is located at a position corresponding to an antinode in quantum state

1402

of the channel over which it is intended to transmit information, and at a node in quantum state

1400

over which it is not intended to transmit information. Similarly, a second receiver

1502

should be placed at the antinode of the quantum state

1402

being modulated by second transmitter

1500

and at a node in quantum state

1400

over which it is not intended to receive information. This embodiment of the present invention therefore illustrates the exploitation of the orthogonality of quantum wavefunctions to enable multiple channels of information to be transferred simultaneously through the same volume of space without crosstalk. Quantum states

1400

and

1402

are designed to have the property of having locations where one state's antinode is at the position of the node of the other state, and vice versa.

Other geometries may also be candidates for multiple channel communication systems. For example, in

FIG. 17

a schematic diagram of a pair of crossed elliptical quantum corral resonators

1700

is shown. Each ellipse in

FIG. 17

may have its own transmitter

102

and receiver

106

simultaneously communicating information through two independent channels in the same region of space. Similarly, single resonators having nearly degenerate eigenstates may also perform the same function. At least one quantum state

104

is required for each channel of information.

The present invention is not limited to systems having the same number of transmitters

102

as receivers

106

. Similarly, more than two information transfer channels may be incorporated into a communication system; for example, different types of quantum state

104

modulation and detection may be simultaneously employed in a particular transfer channel. Information may therefore be simultaneously transferred through a transfer channel in either direction.

Further, computer software may assist in the design of resonators to produce a particular set of quantum states

104

desired for a particular communication system. For example, a designer may specify the initial eccentricity and length of an elliptical resonator and the distribution of nodes and antinodes desired. A computer program may then compute the quantum state

104

density distributions available in the resonator given those parameters, and may then compare the coordinates of the computed nodes and antinodes to the distribution desired. The computer program may then selectively alter the eccentricity and length (or other relevant parameters) so that the resulting quantum states

104

better fit the designer's specifications.

Referring now to

FIG. 18

, a schematic diagram of a pair of interconnected elliptical quantum corral resonators

1800

sharing a common focus

1802

is shown according to a third embodiment of the present invention. This structure is designed to have density distributions that are highly peaked in three locations: common focus

1802

, upper focus

1804

, and lower focus

1806

. Transmitters and receivers placed at these locations may modulate and detect modulations, respectively, imposed upon the same quantum state

104

or set of quantum states

104

. The pair

1800

effectively form a processor

1808

that may perform several different functions depending on the placement of transmitters

102

and receivers

106

within its confines.

First, if a transmitter

102

is placed at common focus

1802

, it will effectively project its quantum mechanical signal to receivers

106

placed at both upper focus

1804

and lower focus

1806

(RTR structure) by modulating quantum states

104

spanning the space within processor

1808

. Information arriving at transmitter

102

may therefore be replicated into two identical copies, each arriving simultaneously at spatially distinct receiver locations due to the symmetry of processor

1808

. By placing receivers

106

at upper focus

1804

and lower focus

1806

, the two copies of the modulating information may be transferred out of processor

1808

with no relative phase difference, for further separate use.

Second, if a transmitter

102

is placed at upper focus

1802

and receivers

106

are placed at both common focus

1802

and lower focus

1806

(TRR structure), copies of the transmitting information having different received values dependent on the quantum state density at each receiver

106

may be transferred out of processor

1808

. The signal received at common focus

1802

may for example be an attenuated version of the signal applied by transmitter

102

. The signal received at lower focus

1806

may be a differently-attenuated version of the signal applied by transmitter

102

due to the asymmetric placement of receivers

106

. Although lower focus

1806

is farther from transmitter

102

than is common focus

1802

, this difference in distance does not necessarily mean that the signal received at lower focus

1806

is more attenuated than the signal received at common focus

1802

; the relative values are determined by the specific design of quantum states

104

in processor

1808

.

Third, if a transmitter

102

is placed at upper focus

1804

, a receiver

106

is placed at common focus

1802

, and a second transmitter

1810

is placed at lower focus

1804

(TRT structure), processor

1808

effectively becomes a multifunction gate. The output of receiver

106

will be at some reference value (e.g. zero) if neither transmitter is generating a signal. If exactly one of the transmitters is actively modulating quantum state

104

, receiver

106

will output a corresponding signal, regardless of which transmitter (

102

or

1810

) is active due to the symmetry of processor

1808

. However, if both transmitters

102

and

1810

are active, receiver

106

will produce a different output signal than it would if only one or neither transmitter were activated, due to the dual modulation of quantum state

104

.

For example, suppose that transmitter

102

and second transmitter

1810

, operating separately, produce a signal at receiver

106

having one third the original transmitted signal amplitude. Further, suppose that when transmitter

102

and second transmitter

1810

operate simultaneously, they together produce a signal at receiver

106

having two thirds the original transmitted signal amplitude. Level-detecting circuitry may translate the received signal to effectively enable processor

1808

to behave as a logic gate. Suppose typically that a received value of less than one third produces a logic “0” output. If a recevied threshold value of one third is required to produce a logic “1” output, processor

1808

behaves as an OR gate. Alternately, if a threshold value of two thirds is required to produce a logic “1” output, processor

1808

then behaves as an AND gate. Similarly, if a threshold value of one third is required to produce a logic “1” output, but a received signal value of two thirds then causes a logic “0” output, processor

1808

then behaves as an exclusive-OR (XOR) gate. If one transmitter is always active (e.g. an atom exists at an antinode) in an XOR gate, a logical inverter is the effective result.

Fourth, if a receiver

106

is placed at upper focus

1804

and transmitters

102

and

1810

are placed at the common focus

1802

and lower focus

1806

(RTT structure), processor

1808

becomes a different multifunction gate. The output of receiver

106

will be at some reference value (e.g. zero) if neither transmitter is generating a signal. If exactly one of the transmitters (

102

or

1810

) is actively modulating quantum state

104

, receiver

106

will output a signal that is dependent both on the transmitted signal and on which of the transmitters (

102

or

1810

) is active. However, if both transmitters

102

and

1810

are active, receiver

106

will produce a different output signal than it would in all other cases; this different output signal will not necessarily simply be a summation of both transmitted signals, even factoring in that one transmitter is farther away and may therefore have a different contribution to the overall modulation. Transmitter

102

at common focus

1802

may for example act to partially block or reflect the signal from second transmitter

1810

at lower focus

1806

. Transfer gates, summers, mixers, and NAND gates may thus be readily constructed by those ordinarily skilled in the art.

Additionally, quantum states

104

may be designed to have more than three density distribution peaks. The additional peaks may be used as locations for additional transmitters enabling formation of logical gates with an arbitrary number of inputs.

Alternately, control transmitters may shift the density distribution pattern of quantum states

104

to deliberately move the nodes and antinodes to different spatial locations corresponding to different sets of transmitters and receivers. In this manner, the invention may select different combinations of transmitters and receivers for information transfer, thus the invention may effectively serve as a multiplexer (MUX) device or programmable switching array.

Referring now to

FIG. 19

, a schematic diagram of a pair of parabolic electron reflectors

1900

and

1902

forming a communication system is shown, according to a fourth embodiment of the present invention. A parabola is a locus of points equidistant from a fixed line and a fixed point (focus) not on the line. If a transmitter

102

is placed at the focus

1904

of first parabolic electron reflector

1900

and a receiver

106

is placed at the focus

1906

of second parabolic electron reflector

1902

, information may be transferred some distance between the reflectors through quantum states

104

operably connecting each focus. Some of the modulation will escape, probably more so than in the case of the preferred embodiment because the quantum states

104

are not as well confined. However, this fourth embodiment illustrates that open geometries may also transfer information via modulation of quantum states.

Thus, with the unique and nonobvious structure and method of the present invention, the limitations placed on conventional microelectronics are overcome, and a new paradigm for information and transfer using engineered quantum states is provided.

While the invention has been described in terms of exemplary embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims.