CN113206364B - Quantum signal circulator and quantum chip - Google Patents
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Abstract
The invention discloses a quantum signal circulator and a quantum chip, wherein the chip consists of one or more independent units, and each unit comprises a frequency-adjustable central superconducting quantum bit, three frequency-adjustable microwave resonant cavities and an adjustable inductive coupler. The central superconducting qubit is respectively coupled with the three microwave resonant cavities through the three adjustable inductive couplers, and the coupling strength between the central superconducting qubit and the microwave resonant cavities can be cut off; preparing and reading the state of the microwave resonant cavity by using auxiliary superconducting qubits; the invention uses the central superconducting quantum bit to simultaneously couple three microwave resonant cavities to form a quantum circulator, can complete the control of the transmission direction of quantum signals in the circulator by controlling the central superconducting quantum bit, can realize the transmission of multi-photon quantum states, plays the role of a quantum router, and has great potential application value for realizing quantum computation and quantum information networks.
Description
Technical Field
The invention relates to the field of superconducting quantum chips, in particular to a quantum chip for realizing quantum signal annular transmission based on adjustable coupling quantum bit and a microwave resonant cavity.
Background
Quantum computing is a new computing mode based on quantum mechanics, and the storage capacity of quantum computing on information is far higher than that of a classical computer due to the characteristics of superposition, entanglement and the like of quantum states. And when information stored in different quantum states is responded, the quantum computing can realize real parallel computing, the information computing capability of the quantum computing on a plurality of specific problems is far superior to that of a classical computer theoretically, the quantum superiority is realized, and the superiority on partial problems is proved by experiments.
Because of good integration, manufacturability and controllability, and the gradually-improved quantum computing coherence in recent years, the superconducting quantum computing scheme is one of the physical platforms with the greatest potential for realizing quantum computing, and quantum chips based on superconducting quantum circuits have started to exhibit quantum superiority in terms of specific problems. The basic working principle of the superconducting quantum circuit is that each quantum bit is composed of a superconducting non-resonant sub-circuit, the electromagnetic wave field is quantized in the superconducting circuit, information is stored in different quantum energy states of the electromagnetic wave field, and the core device is a Josephson junction. In addition, the microwave resonant cavity is also an important device, and is an LC resonant circuit, and the energy level of the LC resonant circuit is uniform. On the basis, in order to realize a quantum chip with expandable and variable coupling strength, a circuit structure of a gmon qubit and an adjustable inductive coupler has been proposed in the prior art, wherein the gmon qubit has the properties of adjustable frequency and adjustable coupling strength with the inductive coupler.
In the superconducting quantum circuit regulation technology, mK-level temperature realized in a dilution refrigerator is utilized to meet the environmental requirement of the superconducting circuit, control lines of quantum bits and a resonant cavity are connected layer by layer, and a software and hardware system is utilized to regulate and control the outside. The hardware mainly comprises a high-frequency microwave generator, a customized arbitrary signal generator, a waveform collector, a stable and high-precision voltage source for adding bias voltage and the like. The reading of the qubit is mainly achieved by indirectly and nondestructively reading the quantum state of the qubit by observing the difference of input and output microwave signals caused by the change of the resonant frequency of the reading cavity. The preparation of superconducting quantum bit and initial state of resonant cavity and the regulation and control of coupling strength are completed by the microwave control line and magnetic flux control line of bit, and the specific method is to utilize the line to input microwave modulation signal meeting specific amplitude of its resonant frequency and magnetic flux bias signal of specific time sequence and current.
In recent years, the computing power on a single quantum device has been greatly increased, and a large quantum information processing unit is generally composed of many small quantum processing units. How to handle quantum information transfer and distribution between different quantum processing units is an indispensable part of future quantum networks, and a stable quantum router is required for this. Because the photon transmission speed is high and the influence of decoherence is small, the method has a decisive role in the transmission of long-distance quantum information, and has great scientific and application values for realizing the high-fidelity transmission of multi-photon quantum state information.
The classical circulator is a multi-port device which transmits incident waves entering any port of the classical circulator into the next port according to the direction sequence determined by the static bias magnetic field, and the transmission of electromagnetic waves can only circulate along a single direction. Based on the technology and the classical circulator, the invention provides a quantum chip for realizing the ring transmission of quantum signals based on the adjustable coupling quantum bit and the microwave resonant cavity, the core structure of the quantum chip is that three frequency adjustable microwave resonant cavities are simultaneously coupled with the central superconducting quantum bit through an inductive coupler, the device can realize the bidirectional ring transmission of information, the direction depends on the state of the central superconducting quantum bit, and the quantum chip plays the role of a quantum router.
Disclosure of Invention
The invention aims to design a chip capable of realizing the control of the transmission direction of a quantum signal in a circulator.
The purpose of the invention is realized by the following technical scheme: a quantum signal circulator, comprising: the microwave antenna comprises a central superconducting qubit, three adjustable inductive couplers and three microwave resonant cavities, wherein the central superconducting qubit is coupled with the three microwave resonant cavities through the three adjustable inductive couplers respectively; the coupling strength of the central superconducting qubit and the microwave resonant cavity can be periodically modulated by Floquet (Floquet);
and the control of the quantum signal transmission direction in each quantum signal circulator is completed by controlling the quantum state of the central superconducting quantum bit.
Furthermore, the central superconducting qubit is formed by connecting an Xmon qubit and a geometric inductor in series. The frequency of the central superconducting qubit is adjustable, and independent microwave control lines, magnetic flux control lines and a reading resonant cavity are all configured.
Furthermore, each microwave resonant cavity is coupled with an auxiliary superconducting qubit, so that the preparation and reading of the quantum state of the microwave resonant cavity are realized, and the frequency of the auxiliary superconducting qubit is adjustable.
Furthermore, the microwave resonant cavity is formed by connecting an LC resonant circuit with a direct current superconducting quantum interference device (DC SQUID) in series, and is provided with an independent magnetic flux control line, the frequency of the microwave resonant cavity is adjustable, and the nonlinearity is not more than 2 MHz.
Further, the circuit structure of the adjustable inductive coupler comprises an LC resonant circuit and a josephson junction, the LC resonant circuit being in series with the josephson junction. The adjustable inductive coupler is provided with an independent magnetic flux control line, the coupling strength between the central superconducting qubit and the microwave resonant cavity can be changed by adjusting the magnetic flux passing through the adjustable inductive coupler, the adjusting range exceeds 30MHz, the coupling strength of the adjustable inductive coupler can be adjusted to 0MHz, and the coupling between the central superconducting qubit and the microwave resonant cavity is closed.
Further, each of the auxiliary superconducting qubits has control and read circuitry comprising: the independent microwave control line is used for preparing the initial state of the superconducting qubit; an independent flux control line for independently adjusting the frequency of each superconducting qubit; a separate read resonator for reading the state of each superconducting qubit.
Further, the size of the quantum signal circulator is in the micrometer scale. The central superconducting qubit, the microwave resonant cavities and the adjustable inductive coupler are integrally arranged in a cross shape, and the three resonant cavities are arranged in a T shape.
Further, the working conditions required for controlling the transmission direction of the quantum information in the circulator are as follows: the three microwave resonant cavities and the central superconducting qubit are in resonance, and the coupling strength g between the microwave resonant cavities and the central superconducting qubitjModulated by an adjustable inductive coupler to meet the requirement
Wherein j is 1,2,3, upsilondIndicates the coupling strength giModulation frequency of g0Denotes the modulation amplitude, t denotes the modulation time, and j is the cavity number.
Further, the control mode of the information transmission direction in the quantum signal circulator is as follows: when a quantum signal is present in any one of the three commonly coupled microwave resonant cavities, this cavity is said to be R1When the central superconducting qubit is in the ground state, the transmission direction of the quantum signal is to modulate the phase difference for the coupling intensity
Cavity 2R2Then difference in phase
Cavity 3R3Namely: r1→R2→R3(ii) a When the central superconducting qubitWhen the quantum well is in an excited state, the transmission direction of the quantum information state is reversed, namely: r1→R3→R2(ii) a When the central superconducting qubit is in the superposition of the ground and excited states, the quantum information state can be simultaneously selected from R1To R2And R3。
The invention also provides a quantum chip which comprises one or more quantum signal circulators, and the information transmission direction is controlled by controlling the quantum state of the central superconducting quantum bit in the quantum signal circulators.
The invention has the beneficial effects that: the invention uses the adjustable inductive coupler containing the Josephson node to realize the periodic modulation of the coupling strength between the microwave resonant cavity and the central superconducting qubit within a certain positive and negative range, the modulation keeps the variation of the coupling strength between different resonant cavities to maintain a specific phase difference of 2 pi/3, the time reversal symmetry is broken, the function of a quantum signal circulator is realized, and the transmission direction of the quantum signal circulator depends on the quantum state of the central superconducting qubit. The invention simultaneously realizes the functions of adjustable central superconducting quantum bit frequency, adjustable microwave resonant cavity frequency and adjustable coupling strength between the central superconducting quantum bit and the three microwave resonant cavities, plays an important role in promoting the development of quantum computation and quantum information, and has great scientific research and industrial application values.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below, and it is apparent that the drawings in the following description only relate to some embodiments of the present invention and are not limiting on the present invention.
FIG. 1a is a schematic diagram of a superconducting quantum chip according to an embodiment of the present invention;
FIG. 1b is a schematic diagram of a superconducting quantum chip of an embodiment of the present invention, the central superconducting qubit of FIG. 1 a;
FIG. 1c is a schematic diagram of a superconducting quantum chip of the embodiment of the present invention illustrating the microwave cavity of FIG. 1 a;
FIG. 1d is a schematic diagram of a superconducting quantum chip of the embodiment of the present invention FIG. 1a auxiliary superconducting qubit and its read circuitry;
FIG. 1e is a schematic diagram of a superconducting quantum chip of the embodiment of the present invention, the inductive coupler of FIG. 1 a;
fig. 2 is a schematic diagram of a circuit structure of the quantum signal circulator.
Wherein the reference numbers indicate:
101. a central superconducting qubit; 102. a microwave resonant cavity; 103. an inductive coupler; 104. an auxiliary superconducting qubit; 105. an air bridge; 106. a coplanar capacitor; 107. a superconducting quantum interference device (SQUID) with a central superconducting qubit; 108. reading a resonant cavity; 109. a coplanar microwave control line; 110. a ground line; 111. a flux control line for the central superconducting qubit; 112. superconducting quantum interference devices (SQUIDs) for microwave resonators; 113. superconducting quantum interference devices (SQUIDs) that assist in superconducting qubits; 114. reading the transmission line; 115. a magnetic flux control line of the microwave resonant cavity; 116. a josephson junction of an inductive coupler; 117. a magnetic flux control line of the inductive coupler; 118. a ground plane.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings. It should be noted that in the drawings or description, the same drawing reference numerals are used for similar or identical parts. Implementations not depicted or described in the drawings are of a form known to those of ordinary skill in the art. Additionally, while the present disclosure may provide examples of parameters that include particular values, it should be appreciated that the parameters need not be exactly equal to the corresponding values, but rather approximate the corresponding values within acceptable error tolerances or design constraints. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
The invention provides a quantum chip for realizing quantum signal annular transmission based on adjustable coupling quantum bits and microwave resonant cavities, wherein the chip is formed by coupling a central superconducting quantum bit with three microwave resonant cavities through three adjustable inductive couplers respectively, periodically modulating the coupling strength between the central superconducting quantum bit and each resonant cavity by a Floquet method, and controlling the quantum signal transmission direction in a circulator by controlling the state of the quantum bit.
The central superconducting qubit is of a gmon type, has adjustable frequency, and is coupled with three microwave resonant cavities through three inductive couplers, and the coupling strength of the central superconducting qubit is adjustable. The coupling strength between the central superconducting qubit and the three microwave resonant cavities is adjustable, and the adjustment range exceeds 30 MHz.
The microwave resonant cavity is formed by connecting an LC loop and a small-inductance Josephson junction in series, the nonlinearity of the microwave resonant cavity does not exceed 2MHz, and the influence can be ignored.
The three microwave resonant cavities are respectively provided with an auxiliary superconducting quantum bit; the auxiliary superconducting qubit and the microwave resonant cavity are coupled through capacitance, the coupling strength is influenced by the frequency of the auxiliary superconducting qubit and the microwave resonant cavity, and the coupling strength is dozens of MHz. The state information of the microwave resonant cavity can be prepared and read through the auxiliary superconducting qubit.
The central superconducting qubit and the auxiliary superconducting qubits each having control and read circuitry comprising: the independent microwave control line is used for preparing the initial state of the superconducting qubit; an independent flux control line for independently adjusting the frequency of each superconducting qubit; a separate read resonator for reading the state of each superconducting qubit.
The microwave cavities have independent flux control lines for independently adjusting the frequency of each microwave cavity, with a modulation range encompassing 4-5 GHz.
The inductive couplers have independent flux control lines for independently adjusting the coupling strength between the microwave resonant cavity coupled by each coupler and the central superconducting qubit.
The three microwave resonant cavities and the central superconducting quantum bit can respectively adjust the frequency, so that the requirement of resonance during quantum signal transmission is met. The modulation of the coupling strength between the three microwave resonant cavities and the central superconducting qubit can realize the periodic realization of any frequency. The interaction between the central superconducting qubit and the microwave resonant cavity can be closed and opened at will, thus realizing more functions. An air bridge airbridge is arranged above all the control and reading circuits so as to ensure the ideal grounding property of the chip. Under the resonance condition of the three microwave resonant cavities and the central superconducting qubit, the coupling strength of the three microwave resonant cavities and the central superconducting qubit can complete Floquet method periodic modulation within the amplitude of plus or minus 15 MHz. The quantum states in the three microwave resonant cavities can realize initial state preparation and indirect reading through the coupling quantum bits, and the condition of more photon numbers can be met. When the three microwave resonant cavities and the central superconducting qubit are in resonance, the bidirectional annular transmission control of information can be realized by controlling the state of the central superconducting qubit through the modulation of the coupling strength.
The embodiment of the invention provides a main structure of a single independent quantum signal circulator, the device is prepared by adopting a superconducting quantum circuit preparation method, and a figure 1a is a structural diagram of the quantum signal circulator. Fig. 1b to 1d provide an illustration of a central superconducting qubit, a microwave resonant cavity, and an inductive coupler, respectively. FIG. 1a is a schematic diagram of a quantum signal circulator. The quantum signal circulator is formed by coupling three frequency-adjustable microwave resonant cavities 102 with a central superconducting qubit 101 through three inductive couplers 103, respectively, each microwave resonant cavity having an independent auxiliary superconducting qubit 104 for preparing and reading the state of the microwave resonant cavity. All of the structures in fig. 1a are formed from superconducting thin film materials (e.g., aluminum or niobium, etc.) fabricated using standard thin film fabrication processes on dielectric substrates (e.g., semiconductor materials such as sapphire, silicon dioxide, or silicon).
The central superconducting qubit 101 of the present embodiment is of the gmon type and, as shown in fig. 1b, comprises a coplanar capacitor 106 and a superconducting quantum interference device (SQUID)107 connected to the capacitor. Coplanar planar capacitor 106 is surrounded by aluminum line 101 and ground plane 118 to form a capacitor. Coplanar planar capacitor 106 forms a series circuit with superconducting quantum interference device 107. The ground line 110 for the central superconducting qubit is routed around three loops and then back to ground near the superconducting quantum interference device, where it is coupled to the inductive coupler 103. The central superconducting qubit has a separate flux control line 111, a coplanar microwave control line 109 and a separate read resonator 108. An external circuit applies external magnetic flux to the superconducting loop through flux control line 111, which changes the inductance of superconducting quantum interference device 107, thereby changing the frequency of the central superconducting qubit, and the head of the flux control line is grounded. The external control circuit provides a microwave resonant in frequency with the central superconducting qubit via the coplanar microwave control line 109, which is surrounded by ground, for initial state preparation and single-bit logic gate operation of the superconducting qubit. The read resonator 108 is capacitively coupled to the central superconducting qubit, and its frequency is influenced by the state of the central superconducting qubit, which is the same as the read resonator for the auxiliary superconducting qubit (see below). The location of air bridges 105 is shown merely as an illustration, and more air bridges may be bridged elsewhere on the chip for better grounding.
In this embodiment, the microwave cavity 102 has one end capacitively coupled to the auxiliary superconducting qubit 104 and one end connected in series to a superconducting quantum interference device 112 and then grounded to form a λ/4 cavity, as shown in fig. 1 c. A magnetic flux control line 115 of the microwave resonant cavity is connected and wrapped around the superconducting interference device 112 through an air bridge, and magnetic flux in the superconducting interference device 112 is changed through the magnetic flux control line 115, so that inductance of the superconducting quantum interference device 112 is changed, and frequency of the microwave resonant cavity is changed. The superconducting quantum interference device 112 has very low inductance, and thus has a nonlinearity of about 2MHz less, for protection of the microwave cavity. A middle portion of the microwave cavity is coupled to an inductive coupler (see below). FIG. 1d is a schematic diagram of an auxiliary superconducting qubit and its read circuitry. The microwave cavity 102 is capacitively coupled to the auxiliary superconducting qubit 104, and the auxiliary superconducting qubit 104 is used to prepare and read the state of the microwave cavity. The auxiliary superconducting qubit 104 has a separate magnetic flux control line 111, a coplanar microwave control line 109 and a separate read resonator 108. The magnetic flux control line 111 changes the frequency of the auxiliary superconducting qubit by changing the magnetic flux of the superconducting quantum interference device 113, and when the auxiliary superconducting qubit resonates with the microwave resonant cavity, photons of the auxiliary superconducting qubit can be transferred into the microwave resonant cavity; or when certain photons exist in the microwave resonant cavity, the photons interact with the auxiliary superconducting qubit, and the microwave resonant cavity transmits information to the auxiliary superconducting qubit. The auxiliary superconducting qubit 104 is capacitively coupled to the read resonator 108, and the end of the read resonator 108 has a curved shape and is coupled to the read transmission line 114. The frequency of the read cavity 108 is related to the state of the auxiliary superconducting qubit, and the frequency of the read cavity 108 can be detected by measuring the microwave scattering parameter S21 of the read transmission line 114, thereby obtaining state information of the auxiliary superconducting qubit.
Fig. 1e is a schematic diagram of an inductive coupler. The inductive coupler 103 is in the shape of an '8' with one end coupled to the central superconducting qubit 101 and one end coupled to the microwave cavity 102. As shown in the figure, the left end of the inductive coupler 103 is wrapped by 2 circles, wherein parts of the inductive coupler are connected through an air bridge 105, a grounding wire 110 of the central superconducting qubit is wrapped in the middle, and a mutual inductance M is generated between the inductive coupler and the central superconducting qubit1(ii) a The right end of the inductive coupler 103 is wrapped by two circles to couple with the microwave resonant cavity, and similarly, the inductive coupler is wrapped by 2 circles to surround the microwave resonant cavity in the middle, and a mutual inductance M is generated between the inductive coupler and the microwave resonant cavity2. The inductive coupler 103 is connected in series with a single josephson junction 116 in the middle and then grounded. The inductive coupler 103 has an independent magnetic flux control line 117, and an external circuit controls the external magnetic flux through the magnetic flux control line 117 to change the inductance of the inductive coupler loop, thereby achieving the purpose of changing the coupling strength of the central superconducting qubit and the microwave resonant cavity.
Fig. 2 is a schematic diagram of a circuit structure of the quantum signal circulator. L isqjEquivalent inductance, L, produced by a superconducting quantum interference device with a central superconducting qubitqA geometric inductance of a central superconducting qubit; l iscIs the geometric inductance, L, of an inductive couplercjIs the equivalent inductance produced by a single josephson junction of the inductive coupler; l isRjIs the equivalent inductance generated by the superconducting quantum interference device of the microwave resonant cavity. Regulating magnetic flux through an inductive coupler
The calculation formula of the coupling strength of the central superconducting qubit and the microwave resonant cavity is as follows:
wherein ω isresonatorIs the frequency, phi, of the microwave resonant cavity0Is the unit magnetic flux.
The implementation of the quantum signal circulator function depends on the effective Hamiltonian:
wherein
giRepresenting a microwave cavity RiThe magnitude of the coupling strength with the central superconducting qubit,dis the coupling strength giThe modulation frequency of (d);+and σ-Up and down operators for the central qubits;
and aj(j ═ 1,2,3) is the microwave cavity generation and annihilation operator. Central superconducting qubit and three microwave resonators RiAnd (4) resonating. If in the microwave cavity R1In the intermediate preparation initial state, when the central quantum bit is in the ground state, the transmission direction of the photon is R1→R2→R3(ii) a When the bit is in the excited state, the photon has a transmission direction R1→R3→R2(ii) a Photons from the microwave cavity R when the bit is in the superposition of the ground and excited states1While transferring to the cavity R2And a cavity R3In (1). The control of the information transmission direction of the quantum circulator is realized by the state of the central superconducting quantum bit, and the bidirectional ring of information can be realized.
The above-described embodiments are intended to illustrate rather than to limit the invention, and any modifications and variations of the present invention are within the spirit of the invention and the scope of the appended claims.
Claims (10)
1. A quantum signal circulator, comprising: the microwave antenna comprises a central superconducting qubit, three adjustable inductive couplers and three microwave resonant cavities, wherein the central superconducting qubit is coupled with the three microwave resonant cavities through the three adjustable inductive couplers respectively; the coupling strength of the central superconducting qubit and the microwave resonant cavity can be periodically modulated by Floquet (Floquet);
the central superconducting quantum bit comprises a coplanar capacitor and superconducting quantum interference equipment connected with the capacitor; the coplanar plane capacitor is surrounded by the ground plane to form a capacitor; the coplanar planar capacitor and the superconducting quantum interference device form a series circuit; the grounding wire of the central superconducting quantum bit is wound around the three rings, then returns to the vicinity of the superconducting quantum interference device to be grounded and is coupled with the inductive coupler; the central superconducting qubit is provided with an independent magnetic flux control line, a coplanar microwave control line and an independent reading resonant cavity;
one end of the microwave resonant cavity is capacitively coupled with the auxiliary superconducting quantum bit, and the other end of the microwave resonant cavity is grounded after being connected with a superconducting quantum interference device in series to form a lambda/4 resonant cavity;
the inductive coupler is in an 8-shaped shape, one end of the inductive coupler is coupled with the central superconducting quantum bit, and the other end of the inductive coupler is coupled with the microwave resonant cavity; the left end of the inductive coupler is wrapped by two circles, wherein parts of the inductive coupler are connected through an air bridge to wrap the grounding wire of the central superconducting qubit in the middle, and a mutual inductance M is generated between the inductive coupler and the central superconducting qubit1(ii) a The right end of the inductive coupler is wrapped by two circles to be coupled with the microwave resonant cavity, the microwave resonant cavity is wrapped by the two circles of the inductive coupler, and the inductorA mutual inductance M is generated between the coupler and the microwave resonant cavity2(ii) a The inductive coupler is connected with a single Josephson junction in series at the tail end and then grounded; and the control of the quantum signal transmission direction in each quantum signal circulator is completed by controlling the quantum state of the central superconducting quantum bit.
2. The quantum signal circulator of claim 1 wherein the central superconducting qubit is a Xmon qubit in series with a geometric inductor; the frequency of the central superconducting qubit is tunable.
3. The quantum signal circulator of claim 1 wherein each microwave cavity is coupled to an auxiliary superconducting qubit to enable preparation and readout of quantum states of the microwave cavity, and wherein the auxiliary superconducting qubit is tunable in frequency.
4. The quantum signal circulator of claim 1 wherein said microwave cavity is an LC resonant circuit in series with a direct current superconducting quantum interference device (DC SQUID) and has independent flux control lines with tunable frequencies and non-linearities of no more than 2 MHz.
5. The quantum signal circulator of claim 1 wherein the circuit structure of the adjustable inductive coupler comprises an LC resonant circuit and a josephson junction, the LC resonant circuit being in series with the josephson junction; the adjustable inductive coupler is provided with an independent magnetic flux control line, the coupling strength between the central superconducting qubit and the microwave resonant cavity can be changed by adjusting the magnetic flux passing through the adjustable inductive coupler, the adjusting range exceeds 30MHz, the coupling strength of the adjustable inductive coupler can be adjusted to 0MHz, and the coupling between the central superconducting qubit and the microwave resonant cavity is closed.
6. The quantum signal circulator of claim 3 wherein each of the auxiliary superconducting qubits has control and read circuitry comprising: the independent microwave control line is used for preparing the initial state of the superconducting qubit; an independent flux control line for independently adjusting the frequency of each superconducting qubit; a separate read resonator for reading the state of each superconducting qubit.
7. The quantum signal circulator of claim 1 wherein the size of the quantum signal circulator is on the order of microns; the central superconducting qubit, the microwave resonant cavities and the adjustable inductive coupler are integrally arranged in a cross shape, and the three resonant cavities are arranged in a T shape.
8. The quantum signal circulator of claim 1 wherein the operating conditions required to control the direction of quantum information transfer within the circulator are: the three microwave resonant cavities and the central superconducting qubit are in resonance, and the coupling strength g between the microwave resonant cavities and the central superconducting qubitjModulated by an adjustable inductive coupler to meet the requirement
Wherein j is 1,2,3, upsilondIndicates the coupling strength giModulation frequency of g0Denotes the modulation amplitude, t denotes the modulation time, and j is the cavity number.
9. The quantum signal circulator of claim 8 wherein the direction of information transfer in the quantum signal circulator is controlled by: when a quantum signal is present in any one of the three co-coupled microwave cavities, this cavity is said to be R1When the central superconducting qubit is in the ground state, the transmission direction of the quantum signal is to modulate the phase difference for the coupling intensity
Cavity 2R2Then difference in phase
Cavity 3R3Namely: r1→R2→R3(ii) a When the central superconducting qubit is in the excited state, the transmission direction of the quantum information state is reversed, that is: r1→R3→R2(ii) a When the central superconducting qubit is in the superposition of the ground and excited states, the quantum information state can be simultaneously selected from R1To R2And R3。
10. A quantum chip comprising one or more quantum signal circulators as defined in any one of claims 1-9, wherein the direction of information transfer is controlled by controlling the quantum state of the central superconducting qubit in the quantum signal circulator.
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| CN114692884B (en) * | 2022-05-31 | 2022-10-28 | 浙江大学杭州国际科创中心 | Method, system and device for realizing anti-noise superconducting quantum bit control |
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