Casimir-effect based tunnel transistor utilizing graphene
A quantum device includes an actuator including a graphene material and having a proximal end mounted to an actuator anchor; an electrode disposed on a distal end of the actuator; a quantum dot, configured to localize a single electron, the quantum dot and the electrode disposed within a common vacuum to define a tunneling gap; and a quantum dot anchor, including the graphene material, disposed in a same plane as the quantum dot relative to the electrode. The quantum device may include a modulator configured to emit electromagnetic signaling within a particular frequency range. The graphene material is tuned to increase a Casimir force between the electrode and the quantum dot anchor in response to the electromagnetic signaling. The increased Casimir force causes the actuator to deform to bring the electrode within an electron tunneling range of the quantum dot, or lowers a tunneling barrier on a static electrode.
1 . A quantum device comprising:
a fixed source electrode comprising a graphene material;
a quantum dot configured to localize a single electron, wherein the quantum dot and the fixed source electrode are disposed within a common vacuum to define a tunneling gap; and
a modulator configured to emit electromagnetic signaling within a frequency range, wherein the graphene material is tuned to vary a surface conductivity of the graphene material in response to the electromagnetic signaling, wherein varying the surface conductivity of the graphene material increases a Casimir force across the tunneling gap to increase an electron tunneling probability across the tunneling gap without physical movement of the fixed source electrode.
2 . The quantum device of claim 1 , further comprising:
a substrate; and
an electrode capacitive plate located on the substrate at a position aligned with the fixed source electrode, wherein the electrode capacitive plate is configured to charge the fixed source electrode and cause an electron to tunnel from the fixed source electrode to the quantum dot to store a qubit in the quantum dot.
3 . The quantum device of claim 1 , further comprising:
a substrate; and
a quantum dot capacitive plate located on the substrate at a position aligned with the quantum dot, wherein the quantum dot capacitive plate is configured to verify that an electron has tunneled from the fixed source electrode to the quantum dot and perform mid-circuit non-destructive readout.
4 . The quantum device of claim 1 , wherein the modulator is configured to emit an optical, radio-frequency, or terahertz signal configured to alter a Fermi level of the graphene material to modulate a permittivity tensor of the graphene material.
5 . The quantum device of claim 1 , wherein a Casimir coefficient n is tuned between approximately 1.0 and 0.3 to define idle and active tunneling states respectively.
6 . The quantum device of claim 1 , wherein the quantum device is configured to operate within a cryogenic environment between 1 milliKelvin (mK) and 4 mK.
7 . The quantum device of claim 1 , further comprising:
an electron spin resonance (ESR) readout assembly configured to measure a qubit state by inducing microwave excitation of an electron localized in the quantum dot and to detect a reflected or transmitted signal amplitude without removing the electron from the quantum dot.
8 . The quantum device of claim 7 , further comprising a microwave stripline through which the microwave excitation is applied, wherein the microwave stripline is physically distinct from a capacitive readout plate.
9 . The quantum device of claim 7 , further comprising a cryogenic parametric amplifier or graphene-based low-noise amplifier configured to amplify the reflected or transmitted signal.
10 . The quantum device of claim 7 , wherein the ESR readout assembly is configured to measure a qubit state within 50 nanoseconds and maintain a coherence time of the qubit state that is greater than 1 millisecond.
11 . A quantum system comprising:
a plurality of quantum devices individually including:
a fixed source electrode comprising a first graphene material;
a quantum dot configured to localize a single electron, wherein the quantum dot and the fixed source electrode are disposed within a common vacuum to define a tunneling gap; and
a modulator configured to emit electromagnetic signaling within a particular frequency range, wherein the first graphene material is tuned to vary a surface conductivity of the first graphene material in response to the electromagnetic signaling in a first frequency range, wherein varying the surface conductivity of the first graphene material increases a Casimir force across the tunneling gap to increase an electron tunneling probability across the tunneling gap without physical movement of the fixed source electrode;
a plurality of mediator quantum dots individually positioned between a pair of adjacent quantum dots of the plurality of quantum devices; and
a mediator bus comprising a plurality of mediator bus quantum dots, wherein the mediator bus links pairs of adjacent quantum dots of the plurality of quantum devices through the plurality of mediator quantum dots, wherein the plurality of mediator quantum dots and the mediator bus enable entanglement propagation between non-adjacent qubits stored in the plurality of quantum devices.
12 . The quantum system of claim 11 , wherein the mediator bus and the plurality of mediator quantum dots are configured to propagate entanglement via detuned dispersive ZZ coupling enabled by Casimir-force modulation.
13 . The quantum system of claim 11 , wherein the mediator bus and the plurality of mediator quantum dots are configured to propagate entanglement across multiple left-right qubit pairs through detuned dispersive ZZ coupling enabled by Casimir-force modulation.
14 . The quantum system of claim 11 , wherein the quantum dots of the plurality of quantum devices, the plurality of mediator quantum dots, and the mediator bus individually include a second graphene material, wherein the second graphene material is tuned to increase a dispersive coupling between adjacent quantum devices producing ZZ interaction, in response to electromagnetic signals in a second frequency range, to enable entanglement propagation through detuned dispersive ZZ coupling enabled by Casimir-force modulation.
15 . The quantum system of claim 14 , further comprising:
a plurality of modulators located along the mediator bus, individually configured to emit electromagnetic frequency in the second frequency range.
16 . The quantum system of claim 14 , wherein the plurality of modulators is configured to emit electromagnetic pulses having a phase alignment of less than 10 picoseconds to synchronize the entanglement propagation.
17 . The quantum system of claim 14 , wherein at least one of the first graphene material and the second graphene material comprises an anisotropic or hyperbolic optical medium, and wherein modulation of a permittivity tensor components of the least one of the first graphene material or the second graphene material changes a local density of electromagnetic vacuum modes to modify the Casimir force experienced by the least one of the first graphene material or the second graphene material.
18 . The quantum system of claim 11 , wherein individual ones of the plurality of quantum devices further includes:
a substrate; and
an electrode capacitive plate located on the substrate at a position aligned with the fixed source electrode, wherein the electrode capacitive plate is configured to charge the fixed source electrode and cause an electron to tunnel from the fixed source electrode to the quantum dot to store a qubit in the quantum dot.
19 . The quantum system of claim 11 , wherein individual ones of the plurality of quantum devices further includes:
a substrate; and
a quantum dot capacitive plate disposed on the substrate and aligned with the quantum dot, wherein the quantum dot capacitive plate is configured to capacitively sense an electron occupancy or charge state of the quantum dot, including detection of an electrostatic response associated with an electron present on the quantum dot, and to perform mid-circuit non-destructive readout without removing the electron from the quantum dot.
20 . The quantum system of claim 11 , wherein individual ones of the plurality of quantum devices further includes:
an electron spin resonance (ESR) readout assembly configured to measure a qubit state by inducing microwave excitation of an electron localized in the quantum dot and to detect a reflected or transmitted signal amplitude without removing the electron from the quantum dot, wherein the microwave excitation is applied through a microwave stripline that is physically distinct from a capacitive readout plate to minimize crosstalk.
21 . The quantum system of claim 17 , wherein the anisotropic or hyperbolic optical medium satisfies ε ⊥ <0 and ε ∥ >0 in a mid-infrared regime, producing hyperbolic dispersion.
22 . The quantum system of claim 17 , configured such that modulation of the Casimir force results in at least a two-fold increase of an unmodulated Casimir force across a gap of two to ten nanometers.
23 . The quantum system of claim 17 , configured such that optical modulation produces a response time less than one hundred femtoseconds.
24 . The quantum system of claim 20 , wherein plurality of modulators and the ESR readout assembly are multiplexed to form entangled clusters exceeding three hundred qubits per array.
25 . The quantum system of claim 20 , wherein the quantum system comprises tile-based clusters of approximately three hundred and twenty qubits each, interconnected via mediator-bus lines.