On-chip parametrically coupled circulator with multi-layer mode nesting

Abstract

The present disclosure provides a multi-layer mode nested on-chip parameter coupling circulator, which mainly includes a core resonance unit and a peripheral passive coupling adaptation network. The core resonance unit includes at least three core resonance modes coupled to each other, and the core resonance unit is configured to make the transmission of the input microwave signal obtain non-reciprocity; the peripheral passive coupling adaptation network includes at least three passive coupling links coupled to the core resonance mode respectively, each passive coupling link includes multiple peripheral resonance modes, and the peripheral passive coupling adaptation network is configured to strengthen the coupling between the core resonance mode and the microwave signal, thereby achieving an increase in the overall bandwidth and an increase in the isolation within the passband.

Description

Technical Field

[0001] The present disclosure relates to the fields of resonant circuits, resonators, and quantum computing technology, and in particular to an on-chip parameter coupling circulator with multi-layer mode nesting. Background Art

[0002] Circulators are currently a commonly used noise isolation element in the readout link of superconducting quantum processors. The usual dispersion readout scheme requires coupling the superconducting bit with a microwave resonator. Under the premise that the frequency difference between the two is much greater than the coupling strength, the microwave resonator is excited with a microwave pulse to receive the microwave reflected by the readout cavity coupled with the bit. The size of this microwave signal is at the single photon level. In order to achieve effective detection of the signal, the signal must be amplified in the cryogenic layer to avoid the signal being overwhelmed by thermal noise. In the amplification link, the effect of the first-stage amplifier is the most critical, and the parametric amplifier based on the Josephson junction is generally used as the first-stage amplifier. In order to prevent the high-power pump signal of the parametric amplifier and other intermodulation signals from flowing back to the readout resonant cavity and affecting the performance of the quantum bit, it is necessary to ensure the signal isolation between the parametric amplifier and the readout resonant cavity. At present, circulators are generally used as such high isolation period. At the same time, circulators can also isolate thermal noise transmitted from room temperature. In addition, circulators are also used as a device to control the direction of signal transmission, playing an important role in superconducting quantum computing and various radio frequency systems. However, the existing circulators use ferrites and permanent magnets to generate isolation, which is bulky. As the number of superconducting quantum bits increases, the circulator in the reading link will need to occupy a large amount of installation space, greatly limiting the large-scale expansion of quantum bits. Summary of the invention

[0003] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present disclosure provides an on-chip parameter coupling circulator with multi-layer mode nesting.

[0004] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0005] According to an embodiment of one aspect of the present disclosure, a multi-layer mode nested on-chip parameter coupling circulator is provided, which mainly includes a core resonance unit and a peripheral passive coupling adaptation network. The core resonance unit includes at least three core resonance modes coupled to each other, and the core resonance unit is configured to make the transmission of the input microwave signal obtain non-reciprocity; the peripheral passive coupling adaptation network includes at least three passive coupling links respectively coupled to the core resonance mode, each passive coupling link includes multiple peripheral resonance modes, and the peripheral passive coupling adaptation network is configured to strengthen the coupling between the core resonance mode and the microwave signal, thereby achieving an increase in the overall bandwidth and an increase in the isolation within the passband.

[0006] According to an embodiment of the present disclosure, the at least three core resonance modes are connected via coupling devices of parametric coupling and / or passive coupling.

[0007] According to an embodiment of the present disclosure, the parametrically coupled device is selected from one or any combination of a single DC-SQUID, a DC-SQUID array, an RF-SQUID, or an RF-SQUID array.

[0008] According to the embodiment of the present disclosure, each of the core resonance modes is nestedly connected to a passive coupling link through passive coupling, and each passive coupling link includes a plurality of peripheral resonance modes arranged in multiple layers in stages.

[0009] According to an embodiment of the present disclosure, the passive coupling device is selected from one or any combination of fixed mutual inductance, fixed capacitance, or fixed inductance.

[0010] According to an embodiment of the present disclosure, each peripheral resonance mode includes a capacitor and an inductor connected in parallel.

[0011] According to an embodiment of the present disclosure, each core resonance mode includes a capacitor and an inductor connected in parallel.

[0012] According to an embodiment of the present disclosure, a multi-layer mode nested on-chip parametric coupling circulator includes three mutually coupled core resonance modes, namely, a first core resonance mode, a second core resonance mode, and a third core resonance mode; wherein, the first core resonance mode A1 and the second core resonance mode B1 are coupled through two identical capacitor connections; the first core resonance mode A1 and the third core resonance mode C1 are coupled by a group of RF-SQUID array bridge connections, and the second core resonance mode B1 and the third core resonance mode C1 are coupled by another group of RF-SQUID array bridge connections.

[0013] According to an embodiment of the present disclosure, the AC bias phases of two groups of RF-SQUID array bridges differ by a fixed phase.

[0014] According to the embodiment of the present disclosure, the multi-layer mode nested on-chip parameter coupling circulator also includes: multiple mutual inductance units, coupling capacitors, and bias units. The multiple mutual inductance units are used to achieve coupling between each core resonant mode and the corresponding passive coupling link, or to achieve coupling between multiple peripheral resonant modes in the passive coupling link; the coupling capacitor is used to achieve coupling connection between peripheral resonant modes; the bias unit is used to bias the coupled device; the bias unit includes a microwave AC drive source, a DC drive source, a bias inductor, and a mutual inductance coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0016] Figure 1 A schematic diagram of the composition and coupling principle of the on-chip parameter coupling circulator of multi-layer mode nesting according to an embodiment of the present disclosure;

[0017] Figure 2 A circuit diagram of a multi-layer mode nested on-chip parameter coupling circulator according to an embodiment of the present disclosure;

[0018] Figure 3 A circuit diagram of another multi-layer mode nested on-chip parameter coupling circulator according to an embodiment of the present disclosure;

[0019] Figure 4 A schematic diagram of an RF-SQUID array according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] The present disclosure provides a multi-layer mode nested on-chip parametric coupling circulator, which is based on the parametric coupling mode theory and uses circuit elements such as capacitors that are easy to manufacture in actual experiments as passive coupling devices. A new layer of peripheral resonance mode composed of integrated circuit capacitors and inductors is coupled with the original parametric coupling circulator core resonance mode, and microwave signals are enhanced by mutual driving between resonance modes, thereby achieving an increase in overall bandwidth and an increase in isolation within the passband. The resonance mode in the present disclosure refers to the intrinsic oscillation in the resonator composed of a fixed capacitor and inductor in the circuit.

[0021] Traditional ferrite circulators are bulky, so technicians have developed many integrated circulator design solutions, and parameter coupling circulators are one of them. However, although the existing parameter coupling circulators are highly integrated, the available bandwidth they provide is too small. The current best solution is only about 250MHz. It is impossible to fully cover the frequency range of a readout link, so it has no practical application value at present. Therefore, the present disclosure provides an improved multi-layer mode nested on-chip parameter coupling circulator.

[0022] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0023] In an embodiment of the present disclosure, a multi-layer mode nested on-chip parameter coupling circulator is provided, such as Figures 1 to 4 As shown, the multi-layer mode nested on-chip parameter coupling circulator mainly includes a core resonance unit and a peripheral passive coupling adaptation network. The core resonance unit includes at least three core resonance modes (such as Figure 1The first core resonance mode A1, the second core resonance mode A2, and the third core resonance mode A3 shown in the figure, it should be noted that the number of core resonance modes can be expanded according to actual needs, for example, it can be 4, 5, 6 or more), the core resonance unit is configured to make the transmission of the input microwave signal obtain non-reciprocity; the peripheral passive coupling adaptation network includes at least three passive coupling links respectively coupled to the core resonance modes, and each passive coupling link includes multiple peripheral resonance modes (such as Figure 1 As shown in the figure, A2 and A3 are coupled and connected to the first core resonance mode A1, B2 and B3 are coupled and connected to the second core resonance mode B1, and C2 and C3 are coupled and connected to the third core resonance mode C1. It should be noted that the number of peripheral resonance modes of each passive coupling link can be expanded according to actual needs, for example, 2 as shown in the figure, or 3, 4, 5, 6 or more). The peripheral passive coupling adaptation network is configured to strengthen the coupling between the core resonance mode and the microwave signal, thereby achieving an increase in the overall bandwidth and an increase in isolation within the passband. It should be pointed out that at least three core resonance modes can be the same or different, and are calculated and adjusted according to actual needs. Similarly, the peripheral resonance modes can be the same or different, and are calculated and adjusted according to actual needs.

[0024] In the embodiments of the present disclosure, Figure 1 As shown, the three central core resonant modes A1, B1, and C1 are connected by parametric coupling and / or passive coupling. β is a parameter used to measure the coupling strength between each core mode (A1, B1, and C1), and its specific value can be calculated from the parameters in the circuit (such as capacitance, inductance, etc.). It represents the parameter that measures the coupling strength between the core modes B1 and C1, e is a natural constant, i is an imaginary unit, and Δ represents the phase difference between the couplings.

[0025] The above-mentioned parameter coupling can have various forms, for example, the parameter coupling device is selected from one or any combination of ordinary single DC-SQUID, DC-SQUID array, RF-SQUID, or RF-SQUID array, such as an RF-SQUID array bridge composed of multiple RF-SQUID arrays. The outer layer of the core resonant unit is nested and connected to the peripheral resonant mode through passive coupling. The above-mentioned passive coupling device can be selected from one or any combination of fixed mutual inductance, fixed capacitance, and fixed inductance.

[0026] According to an embodiment of the present disclosure, the at least three core resonant modes are connected via a coupling device of parametric coupling and / or passive coupling. The parametric coupling device is selected from one or any combination of a single DC-SQUID, a DC-SQUID array, an RF-SQUID, or an RF-SQUID array.

[0027] According to an embodiment of the present disclosure, each of the core resonant modes is connected to a passive coupling link through passive coupling nesting, and each passive coupling link includes multiple peripheral resonant modes arranged in multiple layers. The passive coupling device is selected from one or any combination of fixed mutual inductance, fixed capacitance, or fixed inductance.

[0028] According to an embodiment of the present disclosure, each peripheral resonance mode includes a capacitor and an inductor connected in parallel. Each core resonance mode includes a capacitor and an inductor connected in parallel.

[0029] According to the embodiment of the present disclosure, Figure 2 and Figure 3 As shown, the multi-layer mode nested on-chip parameter coupling circulator includes three mutually coupled core resonance modes, namely, a first core resonance mode A1, a second core resonance mode B1, and a third core resonance mode C1; wherein, the first core resonance mode A1 and the second core resonance mode B1 are connected by two identical capacitors C AB The first core resonance mode A1 and the third core resonance mode C1 are connected and coupled by a set of RF-SQUID array bridges, and the second core resonance mode B1 and the third core resonance mode C1 are connected and coupled by another set of RF-SQUID array bridges. The AC biases of the two sets of RF-SQUID array bridges differ by a fixed phase.

[0030] According to the embodiment of the present disclosure, the multi-layer mode nested on-chip parameter coupling circulator also includes: multiple mutual inductance units, coupling capacitors, and bias units. The multiple mutual inductance units are used to achieve coupling between each core resonant mode and the corresponding passive coupling link, or to achieve coupling between multiple peripheral resonant modes in the passive coupling link; the coupling capacitor is used to achieve coupling connection between peripheral resonant modes; the bias unit is used to bias the coupled device; the bias unit includes a microwave AC drive source, a DC drive source, a bias inductor, and a mutual inductance coil.

[0031] In the embodiments of the present disclosure, Figure 2 As shown in the figure, this is an example of a three-port parametric coupled circulator. The letter in the upper right corner of each component in the figure marks the port where the component is located ( Figure 2The letter in the lower right corner indicates the layer of the structure in which the component is located. For example, the core resonance mode A1 is defined as the first layer, the peripheral resonance mode A2 is defined as the second layer, and A3 is defined as the third layer. Indicates that the port is port A, which is in the third layer structure. With capacitor A peripheral resonance mode A3 is formed, which is connected to the capacitor Coupled with external load Z0 through capacitor Coupled with the resonant mode A2. The peripheral resonant mode A2 is connected by mutual inductance M A Coupled with the core resonance mode A1, the resonance mode coupling of the other ports B and C is similar to that of the above-mentioned port A, and will not be repeated here.

[0032] Combination Figure 2 , Figure 3 , Figure 4 As shown, for the three resonant modes A1, B1, and C1, A1 and C1 are connected by a set of RF-SQUID array bridges (such as Figure 4 As shown in the figure, the RF-SQUID array is a special parameter coupling element, L_1, L_2 represent inductors, and L_J represents a Josephson junction; Figure 2 , Figure 3 As shown in the figure, the RF-SQUID array bridge is composed of four RF-SQUID arrays connected crosswise) to complete parameter coupling, while B1 and C1 complete parameter coupling through another group of RF-SQUID (or rf-SQUID) array bridges driven by differential phase. A1 and B1 are connected by capacitor C AB Ordinary passive coupling is performed. The three core resonant modes of the phase-difference parameter coupling device and the passive coupling connection produce the non-reciprocity of the circulator, while the multi-layer nested coupling of the peripheral resonant modes allows the waves in each resonant mode to drive each other under the coupling connection. The microwave propagates along the passive coupling link, and the signal is enhanced by interference, achieving an increase in bandwidth.

[0033] In port A, the load Z0 is connected through the capacitor The peripheral resonance mode A3 of the third layer is coupled and connected, and the peripheral resonance mode A3 is composed of the inductor With capacitor The other end of the parallel connection is grounded, and the capacitor The peripheral resonance mode A2 of the second layer is connected and coupled, and the peripheral resonance mode A2 is composed of capacitors and inductors. With capacitor The other end of the parallel connection is grounded, and the mutual inductance M A Connected to the first core resonance mode A1. The description of ports B and C is similar to the description of port A above. Figure 2 and Figure 3 As shown, the first core resonance mode A1 and the second core resonance mode B1 are connected by two identical capacitors C AB The first core resonance mode A1 and the third core resonance mode C1 are connected and coupled by a set of RF-SQUID array bridges (parametric coupling), and cos(ω p t) of microwave AC driving source and magnitude I b The DC driving source is connected to the mutual inductance coil for biasing. The second core resonant mode B1 and the third core C1 are coupled by another set of RF-SQUID array bridges, but the AC bias component of this set of RF-SQUID array bridges is a fixed phase difference from the previous set of AC bias The above two parameter couplings and one passive coupling constitute the non-reciprocity generating part of the circulator. The third core resonance mode C1 and the second layer peripheral resonance mode C2 are connected by capacitors. Connect coupling, peripheral resonant mode C2 consists of capacitor With inductor Connect in parallel, ground the other end, and use a capacitor Connect to port C external load Z0.

[0034] In the embodiments of the present disclosure, Figure 2 and Figure 3 As shown, there are two specific embodiments of parameter coupling circulators, that is, two biasing routes. The difference between the two is that the layout of the microwave bias unit driving the parameter coupling device is different. Figure 3 The bias circuit shown can alleviate or solve the problem that the external excitation microwave signal interferes with the signal transmitted by the circulator. The bias unit includes a microwave AC drive source, a DC drive source, a bias inductor, and a mutual inductance coil, such as Figure 2 As shown in Figure 2, the bias inductance has little effect on the resonant mode. Figure 3 As shown, by modifying the access position of the bias inductor, the bias unit circuit is changed from being connected in series with the bias inductor and the RFSQUID array bridge to being connected in parallel with the bias inductor and the RFSQUID array bridge, so that the bias unit circuit can provide more precise bias for the parameter-coupled device.

[0035] So far, the embodiments of the present disclosure have been described in detail in conjunction with the accompanying drawings. It should be noted that the implementation methods not shown or described in the drawings or the body of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and ordinary technicians in the field can simply change or replace them.

[0036] According to the above description, those skilled in the art should have a clear understanding of the on-chip parameter coupling circulator with multi-layer mode nesting disclosed in the present invention.

[0037] In summary, the present disclosure provides an on-chip parameter-coupled circulator with multi-layer mode nesting. The parameter-coupled circulator occupies a very small volume, and its own working environment is the same as the normal working environment of the superconducting quantum bit, and can be conveniently placed in the low-temperature layer where the superconducting quantum bit is located. Because of the use of multi-layer resonant mode coupling nesting, the circulator will have a larger bandwidth than the previous parameter-coupled circulator design. Simulation calculations show that the new parameter-coupled circulator has a bandwidth improvement of about 1.5 times compared to the best performance parameters of the previous on-chip integrated circulator.

[0038] It should be noted that, in this document, unless otherwise specified, “a” element is not limited to a single element, but may include one or more elements.

[0039] In addition, in this document, unless otherwise specified, ordinal numbers such as "first" and "second" are only used to distinguish multiple components with the same name, and do not indicate that there is a hierarchy, level, execution order, or process order between them. A "first" component and a "second" component may appear together in the same component, or appear in different components. The presence of a component with a larger ordinal number does not necessarily indicate the presence of another component with a smaller ordinal number.

[0040] In this document, unless otherwise specified, the so-called feature A "or" or "and / or" (and / or) feature B means that A exists alone, B exists alone, or A and B exist at the same time; the so-called feature A "and" (and) or "and" (and) or "and" (and) feature B means that A and B exist at the same time; the so-called "include", "comprise", "have" and "contain" mean including but not limited to these.

[0041] In addition, unless the steps are specifically described or must occur in sequence, the order of the above steps is not limited to the above list, and can be changed or rearranged according to the required design. And the above embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, the technical features in different embodiments can be freely combined to form more embodiments.

[0042] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A multi-layer mode nested on-chip parameter coupling circulator, comprising: A core resonance unit, comprising at least three core resonance modes coupled to each other, wherein the core resonance unit is configured to enable transmission of an input microwave signal to obtain non-reciprocity; The at least three core resonance modes include a first core resonance mode A1, a second core resonance mode B1, and a third core resonance mode C1; the first core resonance mode A1 and the second core resonance mode B1 are connected by two identical capacitors C AB Connection coupling; the first core resonance mode A1 and the third core resonance mode C1 are connected and coupled by a set of RF-SQUID array bridges, and the second core resonance mode B1 and the third core resonance mode C1 are connected and coupled by another set of RF-SQUID array bridges; A peripheral passive coupling adaptation network includes at least three passive coupling links respectively coupled to the core resonant mode, each passive coupling link includes a plurality of peripheral resonant modes; The peripheral passive coupling adaptation network is configured to strengthen the coupling between the core resonant mode and the microwave signal, thereby achieving an increase in the overall bandwidth and an increase in the isolation within the passband; A bias unit is used to bias each group of RF-SQUID array bridges. The bias unit includes a microwave AC driving source, a DC driving source, a bias inductor, and a mutual inductance coil. The mutual inductance coil corresponding to the bias inductor connected to the microwave AC driving source and the mutual inductance coil corresponding to the bias inductor connected to the DC driving source are connected in series and then connected to the two input ends of the RF-SQUID array bridge.

2. According to the multi-layer mode nested on-chip parametric coupling circulator of claim 1, each of the core resonant modes is connected to a passive coupling link through passive coupling nesting, and each passive coupling link includes a plurality of peripheral resonant modes arranged in multiple layers in a step-by-step manner.

3. According to the multi-layer mode nested on-chip parametric coupling circulator according to claim 2, the passive coupling device is selected from one or any combination of fixed mutual inductance, fixed capacitance, or fixed inductance. 4 . The multi-layer mode nested on-chip parametric coupled circulator according to claim 3 , wherein each peripheral resonant mode comprises a capacitor and an inductor arranged in parallel.

5. The multi-layer mode-nested on-chip parametric coupling circulator according to any one of claims 1 to 4, wherein each core resonant mode comprises a capacitor and an inductor arranged in parallel.

6. According to the multi-layer mode nested on-chip parametric coupling circulator of claim 1, the AC biases of the two groups of RF-SQUID array bridges differ by a fixed phase.

7. The on-chip parametric coupling circulator with multi-layer mode nesting according to any one of claims 1 to 6, further comprising: A plurality of mutual inductance units, used to realize coupling between each core resonant mode and a corresponding passive coupling link, or to realize coupling between a plurality of peripheral resonant modes in a passive coupling link; Coupling capacitors are used to achieve coupling connections between peripheral resonant modes.

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