TECHNIQUES FOR TRANSDUCTION AND STORAGE OF QUANTUM LEVEL SIGNALS
Embodiments described herein include systems and techniques for converting (i.e., transducing) a quantum-level (e.g., single photon) signal between the three wave forms (i.e., optical, acoustic, and microwave). A suspended crystalline structure is used at the nanometer scale to accomplish the desired behavior of the system as described in detail herein. Transducers that use a common acoustic intermediary transform optical signals to acoustic signals and vice versa as well as microwave signals to acoustic signals and vice versa. Other embodiments described herein include systems and techniques for storing a qubit in phonon memory having an extended coherence time. A suspended crystalline structure with specific geometric design is used at the nanometer scale to accomplish the desired behavior of the system.
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This application is a continuation under 35 U.S.C. §120 of U.S. Utility Pat. Application No. 17/087,316, filed on Nov. 2, 2020, by Oskar Painter, Jie Luo, Michael T. Fang, Alp Sipahigil, Paul. B. Dieterle, Mahmood Kalaee, Johannes M. Fink, Amdrew Keller, Gregory MacCabe, Hengjiang Ren, and Justin D. Cohen, entitled “TECHNIQUES FOR TRANSDUCTION AND STORAGE OF QUANTUM LEVEL SIGNALS,” which application is a division of U.S. Non-Provisional Pat. Application No. 16/293,455, filed on Mar. 5, 2019, entitled “Techniques for Transduction and Storage of Quantum Level Signals,” which claims priority to U.S. Provisional Pat. Application No. 62/638,817, filed on Mar. 5, 2018, entitled “Integrated Acoustic and Superconducting Quantum Circuits,” U.S. Provisional Pat. Application No. 62/638,829, filed on Mar. 5, 2018, entitled “Silicon-on-insulator-based Platform for Low-loss Superconducting Microwave Circuits,” U.S. Provisional Pat. Application No. 62/652,194, filed on Apr. 3, 2018, entitled “Ultra-Coherent Thin-Film Microwave Acoustic Bandgap Quantum Phonon Memory,” U.S. Provisional Pat. Application No. 62/652,197, filed on Apr. 3, 2018, entitled “Parametric RF-Mems for Advanced Microwave Signal Processing,” and to U.S. Provisional Pat. Application No. 62/652,200, filed on Apr. 3, 2018, entitled “Electro-Opto-Mechanical Crystals: Parametric Metasurfaces for Classical Signal Processing and Thermal Management,” the disclosures of which are hereby incorporated by reference in their entirety for all purposes.
The following regular U.S. patent applications were filed concurrently with U.S. Non-Provisional Pat. Application No. 16/293,455, and the entire disclosure of the applications are incorporated by reference into this application for all purposes:
- Application No. 16/293,455, filed Mar. 5, 2019, entitled “TECHNIQUES FOR TRANSDUCTION AND STORAGE OF QUANTUM LEVEL SIGNALS”;
- Application No. 16/293,457, filed Mar. 5, 2019, entitled “TECHNIQUES FOR BIDIRECTIONAL TRANSDUCTION OF QUANTUM LEVEL SIGNALS BETWEEN OPTICAL AND MICROWAVE FREQUENCIES USING A COMMON ACOUSTIC INTERMEDIARY”; and
- Application No. 16/293,416, filed Mar. 5, 2019, entitled “METAMATERIAL WAVEGUIDES AND SHIELDED BRIDGES FOR QUANTUM CIRCUITS”.
This invention was made with government support under Grant No. PHY1125565 awarded by the National Science Foundation and Grant No(s). FA9550-16-1-0323 & FA9550-15-1-0015 awarded by the Air Force and Grant No. N00014-15-1-2761 awarded by the Office of Naval Research. The government has certain rights in the invention.
BACKGROUNDQuantum computing employs quantum bits called qubits to represent data and is of interest for modeling quantum systems and implementing quantum algorithms including performing complex and/or difficult computing tasks that may be beyond the capability of classical computers. Example computations in which a quantum computer may find application include simulation of quantum systems themselves, modeling of the chemical or biological properties of complex molecules, searching through large data sets, finding approximately optimal solutions to problems with many degrees of freedom, factoring large numbers, or distributing quantum information within a network. Quantum systems can include, for example, particles, atoms, molecules, and materials; dynamics such as chemical reactions may also be modeled. Quantum algorithms can include, for example, Grover’s algorithm to search efficiently through a large dataset. To perform quantum computations, the quantum state of one qubit (or an ensemble of qubits) must be able to modify the quantum state of another qubit or set of qubits. In a canonical quantum computing architecture, this interaction between qubits is mediated via a quantum bus, which is a loose analog to a traditional computing bus in which information is transferred between different parts of a computer.
Superconducting qubits based on Josephson junctions conventionally operate and communicate at microwave frequencies (e.g., 2-10 GHz) using extremely small quantities of energy and each qubit requires specialized coherent excitation and readout structures that also operate at similar frequencies. As the number of qubits in a quantum processor is increased, these characteristics result in complex interconnect and routing schemes that limit scalability of the quantum processor.
Despite the progress made related to the formation of quantum processors, there is a need in the art for improved methods and systems for converting quantum-level signals between optical, microwave, and acoustic forms. There is also a need in the art for improved methods and system for storing qubit quantum states in a memory.
SUMMARYThe described systems and techniques relate to the field of quantum mechanics for particular use in quantum computing. More specifically, systems and techniques are described for converting (i.e., transducing) a quantum-level (e.g., a single photon) signal between an optical signal and a microwave signal using a common acoustic bandgap resonator. Systems and techniques are also described for converting a quantum-level (e.g. a single photon) signal between a microwave-frequency electrical signal (i.e., a photon) and an acoustic signal (i.e., a phonon) for storing in a phonon memory.
A system can be configured to perform particular operations or actions by virtue of having software, firmware, hardware, or a combination of them installed on or incorporated in the system that in operation causes or cause the system to perform the actions. One general aspect includes a system for transducing and storing a qubit signal. The system may include a suspended crystalline transducer for converting the qubit signal between an electrical (e.g., microwave) form and an acoustic form when the suspended crystalline transducer oscillates at a tuning frequency. The system may also include a suspended crystalline structure coupled to the suspended crystalline transducer, the suspended crystalline structure including acoustic cavities chained together, where the acoustic cavities are of differing sizes to store the qubit signal in acoustic form when the suspended crystalline transducer oscillates at the tuning frequency. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.
Implementations may include one or more of the following features. The system may further include suspended crystalline structures, disposed in a geometric design to isolate the acoustic signal, surrounding the suspended crystalline transducer and the suspended crystalline structure. In some embodiments the suspended crystalline transducer includes a piezoelectric material overlay of a second suspended crystalline structure. The piezoelectric material may be, for example, Aluminum Nitride (AlN). In some embodiments, the system may include conductors that are electrically coupled to the piezoelectric material overlay of the second suspended crystalline structure, where the conductors form an interleaved pattern and provide alternating polarity electrical signals to the piezoelectric material to generate an oscillation at the tuning frequency.
In some embodiments, the suspended crystalline transducer includes a second suspended crystalline structure and conductors overlaying the second suspended crystalline structure. In some embodiments, the conductors are configured to form capacitive features. During transduction, the capacitive features may oscillate at the tuning frequency to generate a changing capacitance. The qubit signal in acoustic form may be generated based on the changing capacitance.
In some embodiments, the suspended crystalline transducer and the suspended crystalline structure each include silicon (Si). In some embodiments, the suspended crystalline transducer and the suspended crystalline structure are disposed in a single crystal silicon layer of a Silicon-on-insulator substrate. In some embodiments, the conductor is aluminum. In some embodiments, the qubit signal is swapped between the suspended crystalline transducer and the suspended crystalline structure when the suspended crystalline transducer oscillates at the tuning frequency. Implementations of the described techniques may include hardware, a method or process, or computer instructions usable by the system.
These and other embodiments of the invention along with many of its advantages and features are described in more detail in conjunction with the text below and attached figures.
Unless otherwise indicated, elements using the same indicator number are the same elements between differing figures. For example, phonon memory 115 in
The non-linearity and size of quantum level bits (i.e., qubits) gives rise to specific problems for storage and conversion of the signals between the three wave types (i.e., optical, acoustic, and electrical). Qubits in the acoustic or electrical form are of such small amplitudes (e.g., single photon level) that the qubit may be lost in the thermal noise associated with standard room temperatures (e.g., sixty degrees Fahrenheit). For this reason, the systems that manipulate qubits in electrical or acoustic form typically operate at very cold temperatures (e.g., tens of millikelvin). However, optical waves do not suffer from the effects of thermal noise at room temperature, and optical waves travel much faster (i.e., the speed of light) than acoustic waves.
Embodiments described herein include the systems and techniques for converting (i.e., transducing) a quantum-level (e.g., single photon) signal between the three wave forms (i.e., optical, acoustic, and microwave). A suspended crystalline structure is used at the nanometer scale to accomplish the desired behavior of the system as described in detail herein. Transducers that use a common acoustic intermediary transform optical signals to acoustic signals and vice versa as well as microwave signals to acoustic signals and vice versa.
Embodiments described herein include systems and techniques for storing a qubit in phonon memory having an extended coherence time. A suspended crystalline structure with specific geometric design is used at the nanometer scale to accomplish the desired behavior of the system as described in detail herein.
Prior to discussing embodiments of the invention, it may be helpful to discuss some terms.
A “qubit” is the basic unit of information in a quantum computer. A specific form of qubit can be realized using superconducting microwave circuits employing a Josephson junction which acts as a highly non-linear inductor element. The superconducting qubits typically operate at microwave frequencies between approximately 2 - 10 GHz. That is, their quantum state is represented as a special mixture (called a superposition) of energy states in which the difference in energy corresponds to a frequency in the 2 - 10 GHz range. The energy difference of these qubit states is extremely small, correspondingly to the energy of a microwave-frequency ‘photon’, roughly 5 to 50 micro-electron Volts. As such, each qubit requires special excitation and read-out methods (also operated at microwave frequencies), and must be protected against tiny amounts of electrical noise in the environment. Further, the superconducting qubits can be converted to an acoustic qubit (e.g., single-phonon) or optical qubit (e.g., single-photon), each of which forms has useful properties. For example, an optical qubit may not get “lost” in thermal noise of a room temperature environment like an acoustic or superconducting qubit may. An acoustic qubit is transmitted at much slower rates, which allows for much smaller components for filters and the like. As the number of qubits in a quantum processor is increased, these characteristics result in complex interconnect and routing schemes that limit scalability of the quantum processor.
The three types of waves or signals discussed herein are microwave signals, acoustic signals, and optical signals. Each of these signals are discussed at the quantum-level (e.g., single photons or single phonons). Therefore, microwaves discussed herein generally include microwaves, optical signals discussed herein are generally not visible to the human eye, and acoustic signals as discussed herein are generally not audible to the human ear. Rather, for example, acoustic signals are mechanical vibrations.
The term “quantum-level” refers to the level at which quantum mechanical effects become important. For example, most of the devices and components described herein are very small (e.g., the nanometer scale) and have very low energy (e.g., single photon).
The term “suspended crystalline structure” refers to a type of structure that may be used in creating components described herein. The crystalline structure can be, for example, Silicon, and can be suspended through a process such as that depicted and described with respect to
Optical network 165 may be any suitable optical network. Optical network 165 may be, for example, a single optical fiber cable connecting quantum computers 105 and 110. In some embodiments, optical network 165 may be a complex optical network connecting any number of quantum computers of which quantum computers 105 and 110 are two exemplary quantum computers.
Quantum computers 105 and 110 include phonon memories 115 and 160, electro-acoustic transducers 120a, 120b, 155a, and 155b, acoustic waveguides 125 and 150, opto-acoustic transducers 130 and 145, and optical transceivers 135 and 140. While each of quantum computers 105 and 110 comprise similar components, each may comprise more or fewer components than depicted herein. For example additional or fewer waveguides, including optical waveguides, acoustic waveguides, and electrical conductors may be included in quantum computers 105 and 110. The specific components included in quantum computers 105 and 110 are shown to provide a simplified view for ease of description.
Phonon memories 115 and 160 may be one or more acoustic cavities capable of storing a qubit for some period of time. The phonon memories 115 and 160 discussed herein are ultra-coherent phonon memories. Coherence of phonon memories 115 and 160 may be, for example, up to one (1) second. Phonon memories 115 and 160 use specific geometries to accomplish the ultra-coherency as described in more detail with respect to
Electro-acoustic transducers 120a, 120b, 155a, and 155b may be one or more transducers capable of converting a microwave to an electro-mechanical (e.g., acoustic) wave (and vice versa) at the quantum-level scale. For example, a qubit may be in the acoustic wave form and electro-acoustic transducers 120 and 155 may convert the qubit to a microwave form that may be transmitted on a conductor. Electro-acoustic transducers may be suspended crystalline structures configured with specific geometries as described in more detail with respect to
Acoustic waveguides 125 and 150 may be any quantum level acoustic waveguide capable of propagating a qubit in acoustic format. Acoustic waveguides 125 and 150 may be suspended crystalline structures with specific geometries as described with respect to
Opto-acoustic transducers 130 and 145 may be one or more transducers capable of converting an optical wave to a mechanical (e.g., acoustic) wave (and vice versa) at the quantum-level scale. For example, a qubit may be in the acoustic wave form and opto-acoustic transducers 130 and 145 may convert the qubit to an optical form that may be transmitted via an optical waveguide or over an optical network. Because optical waves, even at the quantum scale, are not substantially impacted by thermal noise, qubits in optical wave form may be manipulated at room temperature. Qubits in acoustic or microwave form are each impacted by thermal noise such that at room temperature the qubit may be lost in the noise. Therefore, qubits in microwave or acoustic form are typically manipulated at very low temperatures (e.g., tens of millikelvin). Opto-acoustic transducers 130 and 150 may be suspended crystalline structures configured with specific geometries as described in more detail with respect to
Optical transceivers 135 and 140 may be any suitable optical device that may send or receive an optical signal at the quantum level. For example, optical transceivers may send and receive optical qubits.
In use, quantum computing system 100 may manipulate one or more qubits to perform quantum computing. As a simplified example for explaining the components herein, a qubit in acoustic form may be stored in phonon memory 115 of quantum computer 105. The electro-acoustic transducer 120a may extract the qubit from the phonon memory 115 as described with respect to
The optical transceiver 135, which may be at room temperature in some embodiments, may transmit the optical qubit to optical transceiver 140 of quantum computer 110. The optical qubit may propagate, for example, via an optical waveguide to opto-acoustic transducer 145. The opto-acoustic transducer 145 may convert the qubit into acoustic form. The acoustic qubit may propagate via acoustic waveguide 150 to electro-acoustic transducer 155b, which may convert the qubit to a microwave form. The qubit may propagate via a conductor to electro-acoustic transducer 155a, which may store the qubit in phonon memory 160.
In some embodiments, quantum processors may further process the qubit within quantum computers 105 and 110. This and many other features of quantum computers 105 and 110 are not shown herein for simplicity.
Transduction Between an Optical Signal and an Acoustic SignalParametric coupling in optomechanics is possible due to the inherent nonlinearity of radiation pressure (the coupling between light and mechanical motion is dependent upon the optical intensity, not the optical field). Confining optical and acoustic energy to the nanoscale results in a nonlinearity that can be many orders of magnitude larger than conventional optical nonlinearities and presents unique capabilities for optical signal control. Opto-acoustic transducer 200 relies on the natural hierarchy of higher frequency optical photons and lower frequency microwave phonons, which have matching spatial wavelength due to the large difference in the speed of light and the speed of sound. This hierarchy, along with the radiation pressure nonlinearity, allows one to use two-photon transitions to couple optical signals to microwave phonon signal. Opto-acoustic transducer 200 is an engineered photonic and phononic bandgap structure which can be “printed” into the thin-film surface layer of a microchip.
Opto-acoustic transducer 200 may be a suspended crystalline structure. Opto-acoustic transducer 200 may be made from, for example, Silicon. As an example, a Silicon-on-insulator (SOI) substrate including single crystal silicon layer can be processed to form opto-acoustic transducer 200 having elements in the single crystal silicon layer. For example, the process used as described with respect to
The opto-acoustic transducer 200 is a nanometer scale device as shown by the scale 220. Such small scale photonic crystals (i.e., the opto-acoustic transducer 200) creates a means to localize light to such a degree that radiation pressure coupling to elastic waves of the dielectric photonic structure is strongly manifest. The physics of mechanical-light interactions in materials, although well understood in the bulk, are quite often much more subtle when more complex geometries are involved, such as the patterned opto-acoustic transducer 200.
The radiation pressure nonlinearity utilized in the opto-acoustic transducer 200 described above is wavelength agnostic. The capacitive forces utilized in micro-electro-mechanical systems (MEMS) and nano-electro-mechanical systems (NEMS) devices are derived from a low frequency version of the optical radiation pressure effect. The opto-acoustic transducer 200 may be created using a silicon-on-insulator (SOI) material platform which has excellent microwave, acoustic, and optical properties. Nanoscale vacuum-gap capacitors with vacuum gaps of less than twenty (20) can be fabricated, which are sufficient to create high impedance microwave resonant circuits capable of strong coupling to RF (e.g., 100 MHz) acoustic resonances.
In the embodiment illustrated in
A unit cell 410 of the capacitive structure 417 is depicted in more detail in
A tuning frequency is set by the size and number of unit cells used in the central nanobeam phononic crystal cavity 415. The unit cells 410 form a ladder shape, and the size of each unit cell must be small enough to generate the high frequencies needed for quantum scale signals. Therefore, dimensions (an, wn, wy, wx) of the unit cell 410 are determined based on the desired tuning frequency for the capacitive electro-acoustic transducer 400. The number of unit cells is selected to generate a capacitance large enough for the bottom and top capacitive features to couple the acoustic and microwave frequency elements. The tuning frequency is the microwave transition frequency of the qubit, also called a qubit frequency.
The oscillation is formed from an acoustic band near the Γ-point at wavevector kx = 0. For a lattice constant of an = 1.55 µm, numerical finite-element method (FEM) simulations place the r-point frequency of the oscillation mode band at ωm/2π = 0.425 GHz. A minimum motional mass (meff) is desired to increase the zeropoint amplitude xzpf= (ℏ/2meffωm)½. In the case of the central nanobeam phononic crystal cavity 415, this corresponds to minimizing both the thickness of the crystalline layer (e.g., silicon) and conductive layer (electrodes 405 and 430, which may be aluminum) and the width of the beam features. Also, a large mechanical capacitance (Cm) is desired, owing to limits on the achievable stray capacitance 420. The use of a Γ-point acoustic mode makes the electromechanical coupling from each unit cell 410 additive, and thus increasing the number of unit cells 410 in the central nanobeam phononic crystal cavity 415 results in an increased mechanical capacitance and participation ratio, η = Cm/(Cm + Cs). Capacitor 420 is dominated by the stray capacitance of the planar spiral coil inductor 425 forming the LC resonator.
Conductors 605 include a conductive material overlaying a suspended crystalline structure. The conductive material may be aluminum. Each of the conductors 605a, b, c, d, e, and f are individual chains of crystalline cavities overlaid by the conductive material. The patterned crystalline structure is configured to block the acoustic signal that emits from the transducer core 615 (i.e., piezoelectric resonator) at its acoustic resonance frequency. The physical design of conductors 605 is implemented in compliance with bandgap engineering techniques to provide the desired mechanical isolation at the acoustic resonance frequency. The conductors 605 a, b, c, d, and e each overlay the transducer core 615, such that they alternate directions. The polarity of the voltages on each of the conductors 605a, b, and c are the same and the polarity of the voltages on each of the conductors 605 d and e are the same and the opposite of the polarity of conductors 605a, b, and c. While five conductors are shown, more or fewer conductors may be used. At transducer core 615, in an exemplary embodiment, the suspended crystalline structure (e.g., single crystal silicon) supports transducer core 615, which, in turn, supports electrically isolated conductors 605 that are operable to apply a spatially varying electric field to the transducer core 615. An alternating polarity on the conductors 605 (e.g., conductors 605a, b, and c may provide a positive voltage and conductors 605d and e may provide a negative voltage) can create a wave effect in the transducer core 615, which, as a result of the piezoelectric properties of the transducer core 615, excites a mechanical oscillation in the transducer core 615. In some embodiments, the silicon chains 606 that do not provide voltage to the transducer core 615 may be removed during the manufacturing process.
The acoustic cavity 610 may be a suspended crystalline structure, and is depicted in more detail in
In use, providing, for example, a positive voltage on conductors 605a, b, and c and a negative voltage on conductors 605e and f, can excite the mechanical oscillation because of the piezoelectric properties of the transducer core 615. The mechanical oscillation is the acoustic form of the microwave signal.
In use, opto-acoustic transducer 200 may convert an optical qubit into an acoustic qubit. The opto-acoustic transducer 200 will oscillate at a frequency associated with the acoustic signal. When the piezoelectric electro-acoustic transducer 600 is tuned to oscillate at a matching acoustic frequency, piezoelectric electro-acoustic transducer 600 can convert the acoustic qubit to superconducting qubit for transmitting on a conductor. The process also works to convert a qubit in microwave form to an acoustic form and then into an optical form.
Method 800 begins at block 805 with a suspended crystalline optical waveguide receiving a single photon optical signal from an optical device. The optical waveguide may be, for example, optomechanical cavity 255. The optical device may be any suitable optical device for transceiving a single-photon optical signal.
At block 810 a first suspended crystalline transducer converts the single photon optical signal to an acoustic signal. The first suspended crystalline transducer may be, for example, opto-acoustic transducer 200. The opto-acoustic transducer oscillates at a tuning frequency to convert the single photon optical signal to a single-phonon acoustic signal. A photon pump may be used to excite the opto-acoustic transducer to oscillate at the tuning frequency.
At block 815 a second suspended crystalline transducer is tuned to oscillate at the tuning frequency. The second suspended crystalline transducer may be, for example, capacitive electro-acoustic transducer 400 or piezoelectric electro-acoustic transducer 600. The second suspended crystalline transducer may be excited by a microwave signal to oscillate at the tuning frequency. When excited to oscillate at the tuning frequency, the second suspended crystalline transducer may obtain or convert the single-phonon acoustic signal from the first suspended crystalline transducer to a single-photon microwave signal. In other words, in response to the tuning, the second suspended crystalline transducer may convert the single-phonon acoustic signal to a microwave signal at block 820.
At block 825, the second suspended crystalline transducer may transmit the microwave signal on a conductor.
Storing a Qubit in a Phonon Memory StructureGigahertz frequency acoustical waves have micron scale wavelengths, five orders of magnitude smaller than electrical waves of the same frequency. As such, storage, readout, and bus cavities in a circuit quantum acoustodynamics (CQAD) architecture can be much more compact than the equivalent in circuit quantum electrodynamics (CQED). Information stored in the acoustical domain is much more effectively isolated because, unlike electrical signals, elastic waves don’t propagate in vacuum. Coupling can only occur within the two-dimensional surface of the chip. Furthermore, the chip can be patterned with a micron-scale periodic structure (i.e., as utilized in the phonon memory) that creates a bandgap in the acoustical spectrum around the frequency of interest. Finally, the size of superconducting qubit circuits is comparable to or larger than acoustical wavelengths; thus, qubits don’t couple to all parts of the acoustic spectrum through structureless dipole coupling, but only to specific wave vectors, chosen at the time of fabrication. As such, neighboring qubits can be effectively decoupled while remote qubits can be strongly coupled through virtual phonon exchange.
Phononic crystals and thin film piezoelectrics in the described architecture have the advantage of mitigating many of the issues associated with current piezo-acoustic technologies, such as Surface Acoustic Wave (SAW), Bulk Acoustic Wave (BAW), and thin-Film Bulk Acoustic Resonator (fBAR) devices. Geometric patterning of a thin surface layer film, such as the silicon device layer of silicon-on-insulator, are used to guide, trap, and diffract microwave acoustic waves with exquisite control, negligible loss, and utilizing small chip real estate. Coupling between the acoustic waves in the acoustic circuitry to electrical elements in the superconducting microwave circuits is realized using the spatially-selective employment of an additional ultra-thin layer of piezoelectric, such Aluminum Nitride in the transducer core. The spatially-selective use of an ultra-thin layer of piezoelectric material reduces acoustic and electrical losses and noise while allowing for significant coupling between the two wave fields.
Acoustic energy damping lifetimes greater than one second (Q = 5 × 1010) are possible in, for example, a 5 GHz frequency silicon oscillator. Mechanical (acoustic) resonators can far exceed, by more than 3-orders of magnitude, the performance of chip-scale microwave components for quantum information storage. This performance boost is made possible due to a forbidden frequency gap (bandgap) that arises for acoustic waves of all polarizations in geometrically patterned thin films (thin-film phononic crystals). The shielding of phononic crystals protects localized phonons from tunneling (clamping loss) and Rayleigh scattering from impurities and defects. The high level of control over the dispersion of the propagation channels also enables dense packing of phononic circuits in various connection topologies while limiting cross-talk in large scale systems.
In the virtual coupling scenario of
As shown in
Detuning can be chosen by considering the desired level of isolation from the mediating resonator. Assuming a superconducting (e.g., transmon) qubit T1 ≈ 100 µs and a LC coil resonator Q-factor of Qe ≈ 5 × 105 (which are typical single-photon numbers on silicon on Insulator), (JA/ Δ) <~ 10-1 may ensure no added dephasing of the qubit by the coil resonator. Similarly, for a T1 ≈ 100 ms for the uncoupled phonon memory and an acoustic Q-factor of Qa ≈ 105 for the piezo-acoustic cavity, (JC/Δ′) <~ 10-2. A suitable detuning in this case, for example, is Δ /2 π ≈ 200 MHz. The corresponding virtual coupling rate is then Jeff ≈ 200 kHz, corresponding to a qubit-to-memory transfer time of Τt <~ 1 µs, far faster than the assumed qubit or memory decoherence time.
The physical implementation shown in
Although only three electrodes 1115, 1117, and 1119 are illustrated in
Referring to
As illustrated in
In one implementation, in order to fabricate the structure illustrated in
The process begins with an initial structure 1305 including a bottom silicon handle having a layer of silicon oxide, over which another layer of silicon is grown, and the top layer is Aluminum Nitride. This is a silicon on insulator substrate.
A dry etch is performed to etch away the unwanted portions of Aluminum Nitride, which is shown at structure 1310. A silicon oxide layer is grown over top of the structure, which is shown at structure 1315. Another dry etch removes the new silicon oxide from portions of the Aluminum Nitride, which is shown at structure 1320. A wet etch is then performed to remove the uncovered and unwanted Aluminum Nitride, which is shown at structure 1325. A second wet etch is performed to remove the remaining top layer of silicon oxide, which is shown at structure 1330. These steps ensure that the top layer of silicon is not damaged in the removal of the Aluminum Nitride.
Once the silicon is exposed having only the desired Aluminum Nitride remaining, a dry etch is performed to create small holes in the silicon at various locations to expose the underlying silicon oxide layer. The holes are approximately 50 nm diameter, and they are patterned into the resist using electron-beam lithography. This step is shown by structure 1335. An aluminum evaporation is performed to place an aluminum conductor over portions of the structure as shown at structure 1340. Josephson junctions and other bandaging is created as shown at structure 1345. Finally, an anhydrous HF vapor release is performed to remove the underlying silicon oxide layer. The anhydrous HF vapor release can undercut the silicon device layer by selectively removing the buried silicon oxide, without attacking the aluminum features and without destroying the Josephson junctions As shown at structure 1350, the top silicon layer is now a suspended crystalline structure.
In some embodiments, the SOI wafer consists of a 220-nm-thick silicon device layer with surface orientation and with a specified resistivity of, for example, >3000 Ωcm. Underneath the device layer is a 3-µm buried silicon dioxide (SiO2) BOX layer. The device and BOX layers sit atop a silicon (Si) handle wafer of thickness 675 µm and a specified resistivity of, for example, 3000 Ωcm. Both the Si device layer and the handle wafer may be grown using the Czochralski crystal growth method. The Si device layer may be grown using the float-zone method.
Each of the calculations or operations described herein may be performed using a computer or other processor having hardware, software, and/or firmware. The various method steps may be performed by modules, and the modules may comprise any of a wide variety of digital and/or analog data processing hardware and/or software arranged to perform the method steps described herein. The modules optionally comprising data processing hardware adapted to perform one or more of these steps by having appropriate machine programming code associated therewith, the modules for two or more steps (or portions of two or more steps) being integrated into a single processor board or separated into different processor boards in any of a wide variety of integrated and/or distributed processing architectures. These methods and systems will often employ a tangible media embodying machine-readable code with instructions for performing the method steps described above. Suitable tangible media may comprise a memory (including a volatile memory and/or a non-volatile memory), a storage media (such as a magnetic recording on a floppy disk, a hard disk, a tape, or the like; on an optical memory such as a CD, a CD-R/W, a CD-ROM, a DVD, or the like; or any other digital or analog storage media), or the like.
Different arrangements of the components depicted in the drawings or described above, as well as components and steps not shown or described are possible. Similarly, some features and sub-combinations are useful and may be employed without reference to other features and sub-combinations. Embodiments of the present disclosure have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. In certain cases, method steps or operations may be performed or executed in differing order, or operations may be added, deleted or modified. It can be appreciated that, in certain aspects of the present disclosure, a single component may be replaced by multiple components, and multiple components may be replaced by a single component, to provide an element or structure or to perform a given function or functions. Except where such substitution would not be operative to practice certain embodiments of the present disclosure, such substitution is considered within the scope of the present disclosure.
It is to be understood that the figures and descriptions of embodiments of the present disclosure have been simplified to illustrate elements that are relevant for a clear understanding of the present disclosure. Those of ordinary skill in the art will recognize, however, that these and other elements may be desirable. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present disclosure, a discussion of such elements is not provided herein. It should be appreciated that the figures are presented for illustrative purposes and not as construction drawings. Omitted details and modifications or alternative embodiments are within the purview of persons of ordinary skill in the art.
It can be appreciated that, in certain aspects of the present disclosure, a single component may be replaced by multiple components, and multiple components may be replaced by a single component, to provide an element or structure or to perform a given function or functions. Except where such substitution would not be operative to practice certain embodiments of the present disclosure, such substitution is considered within the scope of the present disclosure. A recitation of “a”, “an” or “the” is intended to mean “one or more” unless specifically indicated to the contrary.
The examples presented herein are intended to illustrate potential and specific implementations of the present disclosure. It can be appreciated that the examples are intended primarily for purposes of illustration of the present disclosure for those skilled in the art. There may be variations to these diagrams or the operations described herein without departing from the spirit of the present disclosure. For instance, in certain cases, method steps or operations may be performed or executed in differing order, or operations may be added, deleted or modified.
Furthermore, whereas particular embodiments of the present disclosure have been described herein for the purpose of illustrating the present disclosure and not for the purpose of limiting the same, it will be appreciated by those of ordinary skill in the art that numerous variations of the details, materials and arrangement of elements, steps, structures, and/or parts may be made within the principle and scope of the present disclosure without departing from the present disclosure as described in the claims.
APPENDICESThe present disclosure includes Appendix A, the entire contents of which is incorporated herein for all purposes and is considered part of this disclosure.
Claims
1. A system, comprising:
- a mechanical resonator; and
- a circuit coupled to the mechanical resonator;
- wherein the circuit is configured to coherently excite hypersonic mechanical motion of the mechanical resonator so as to transfer a quantum level signal for storage in the mechanical resonator.
2. The system of claim 1, wherein the circuit is configured to coherently excite the hypersonic mechanical motion of the mechanical resonator so as to transfer the quantum level signal for storage in the mechanical resonator with a Q factor of at least 106.
3. The system of claim 1, further comprising a waveguide coupled to the circuit, wherein phonons dissipate from the mechanical resonator via leakage of a photon from the circuit through the waveguide.
4. The system of claim 1, wherein the circuit comprises a microwave circuit, the hypersonic mechanical motion comprises a mode at a gigahertz frequency, and the microwave circuit and the mechanical resonator are coupled via a cooperative coupling of at least 30.
5. The system of claim 1, wherein the circuit comprises a superconducting microwave circuit and the quantum level signal comprises a superposition state.
6. The system of claim 1, wherein the circuit controls a detuning of a drive tone relative to resonant modes of the circuit, so as to control the storage and a readout of the quantum level signal.
7. The system of claim 1, wherein the circuit is configured to define an operating bandwidth of the system.
8. The system of claim 1, wherein the mechanical resonator comprises a nano-mechanical resonator.
9. The system of claim 8 wherein the nano-mechanical resonator comprises a nanobeam.
10. The system of claim 1, wherein the mechanical resonator comprises a chain of acoustic cavities or a linear resonator.
11. The system of claim 1, wherein the mechanical resonator comprises a piezoelectric nanomechanical resonator.
12. The system of claim 1, wherein the mechanical resonator comprises a phononic crystal comprising a phononic bandgap suppressing or eliminating acoustic radiation from the mechanical resonator other than via the circuit.
13. The system of claim 1, wherein the circuit transfers the quantum level signal comprising a qubit suitable for processing in a quantum computer.
14. The system of claim 1, wherein the circuit is configured to readout the qubit stored in the mechanical resonator.
15. The system of claim 1, wherein the circuit is configured to transfer the quantum level signal via a parametric interaction.
16. The system of claim 1, comprising a transducer transducing the quantum level signal between an electrical form in the circuit and an acoustic form in the mechanical resonator.
17. A network comprising the transducer of claim 16, wherein the network distributes quantum information using the quantum level signal.
18. The system of claim 1, comprising a transducer transducing the quantum level signal into an optical signal.
19. A network comprising the transducer of claim 18, wherein the network distributes quantum information using the optical signal.
20. The system of claim 1, further comprising a metamaterial.
21. A method of storing quantum level signals, comprising:
- coherently exciting a hypersonic mechanical motion of a mechanical resonator, so as to transfer a quantum level signal for storage in the mechanical resonator with a Q factor of at least 106; and
- removing phonons from the mechanical resonator via leakage of photons from a circuit coupled to the mechanical resonator.
Type: Application
Filed: Mar 21, 2023
Publication Date: Jul 20, 2023
Applicant: California Institute of Technology (Pasadena, CA)
Inventors: Oskar Painter (Sierra Madre, CA), Jie Luo (Pasadena, CA), Michael T. Fang (Pasadena, CA), Alp Sipahigil (Pasadena, CA), Paul B. Dieterle (Somerville, MA), Mahmoud Kalaee (Pasadena, CA), Johannes M. Fink (Klosterneuburg), Andrew J. Keller (Los Angeles, CA), Gregory MacCabe (Los Angeles, CA), Hengjiang Ren (Pasadena, CA), Justin D. Cohen (Annandale, VA)
Application Number: 18/187,419