CN218446727U - Lumped control line and quantum chip - Google Patents

Abstract

The application discloses lumped control line and quantum chip belongs to the quantum chip field of making. The control lines include control lines and couplers. The lumped control line can be used in a quantum chip with multiple bit numbers to control the quantum bit. In the corresponding quantum chip, the number of pins for connecting the required lines is small, so that the number of lead bonding is reduced, and the difficulty in packaging the chip is reduced.

Description

Lumped control line and quantum chip

Technical Field

The application belongs to the field of quantum chip preparation, and particularly relates to a lumped control line and a quantum chip.

Background

Generally, the leads in a superconducting quantum chip can be divided into: read lines (e.g., bus), control lines (e.g., XY control lines, and Z control lines). With the increasing number of qubits in the superconducting quantum chip, the number of quantum chip pins related to the leads is also increasing, thereby increasing the difficulty in manufacturing the quantum chip.

Because the superconducting quantum chip and the measurement and control circuit board thereof need to be connected in a mode of bonding through the aluminum wires, the more the pins of the superconducting quantum chip are, the more the number of the needed bonding aluminum wires is, and the packaging efficiency of the chip is reduced.

On the other hand, the size of the processable wafer is limited by the equipment and is difficult to be made large, so that the size of the quantum chip is difficult to be made small as the number of pins of the superconducting quantum chip is increased.

Therefore, it is necessary to optimize the lead design in the quantum chip to reduce the number of leads, thereby controlling the number of bonding aluminum wires and improving the chip size and the packaging efficiency thereof.

SUMMERY OF THE UTILITY MODEL

In view of the above, the present application discloses a lumped control line and a quantum chip. The lumped control line can be applied to a quantum chip, and is connected with an external circuit for signal input by using a smaller number of pins, so that the number of lead wires is correspondingly reduced, the packaging efficiency is improved, and the chip size is reduced.

The scheme exemplified in the present application is implemented as follows.

In a first aspect, examples of the present application propose a lumped control line. It comprises the following steps: a control circuit having an extended trace, the control circuit defining coupling regions distributed along the extended trace; and

and a coupler, and one end of the coupler is coupled with the coupling region of the control circuit, and the other end of the coupler is configured to be coupled with the qubit.

According to some examples of the present application,

the number of the coupling areas is at least two, and all the coupling areas are spaced along the extending track of the control circuit;

the number of the couplers is at least two, and each coupler is independently configured at intervals;

the coupler, qubit and coupling region have the following correspondence:

one coupler corresponds to one qubit and one coupling region and different couplers correspond to different qubits and different coupling regions.

According to some examples of the application, the control circuit is a linear structure;

and/or the control circuit is a coplanar waveguide transmission line;

and/or the coupler is a coplanar waveguide resonant cavity.

According to some examples of the application, the coupler is a coplanar waveguide having two ends, a ground end and an open end, respectively.

According to some examples of the application, the coupler is a half-wavelength resonator;

and/or the number of the couplers is multiple, and the length of each coupler is different, so that the original microwave signal fed by the control circuit forms a target microwave signal matched with the corresponding coupler after being filtered by the couplers.

According to some examples of the application, the coupler has a coupling portion, and the coupling portion extends parallel to the control circuit, and the ground terminal is located at the coupling portion.

According to some examples of the application, the coupler is serpentine between the coupling portion and the open end.

According to some examples of the present application, the coupler has at least one non-bent section and a plurality of bent sections between the coupling portion and the open end, and adjacent bent sections are connected by the non-bent section.

In a second aspect, some examples of the present application propose a quantum chip. It includes:

a plurality of qubits; and

the aforementioned lumped control line;

the coupler in the lumped control line is coupled to the qubit.

According to some examples of the application, some or all of the qubits are arranged in a one-dimensional chain and coupled two by two in sequence;

and/or the lumped control line is arranged in a coplanar manner with the qubit;

and/or the control circuit is disposed coplanar with the qubit.

According to some examples of the application, the qubits are computational qubits and adjacent computational qubits are coupled by coupling qubits.

According to some examples of the application, the frequency of the coupled qubits is tunable.

Has the advantages that:

the lumped control line takes the control circuit as a channel for transmitting an externally input control signal and then transfers the control signal to a qubit coupled with the control circuit through the coupler. That is, the lumped control lines may utilize a control circuit to distribute signals to the various couplers for retransmission to the qubits coupled to the couplers. Thus, each coupler does not need to be externally input with a control signal, and accordingly does not need to be independently configured with an intermediate structure such as a pin for connection with the outside.

In combination with the above, when the lumped control line is applied to a quantum chip, the lumped control line may be connected to signals of an external circuit, a system, and the like through pins, and the coupler does not need to be configured with pins, so that the number of pins required to be configured may be reduced.

Unlike a scheme in which a control signal line connected to an external circuit using a pin is independently configured for each qubit in a qubit chip, the lumped control line in the example of the present application has a control circuit and a coupler as a transmission channel of a control signal between the external circuit of the chip and the qubit in the chip. The control circuit and the external circuit can be connected through the pins through the leads, and the coupler does not need to be provided with the pins, the leads and other structures independently. Therefore, the lumped control line in the example can effectively reduce the number of pins required to be configured when the lumped control line is applied to the chip, and further can control the number of lead wires corresponding to the pins, so that the packaging efficiency of the chip can be controlled, and the size of the packaged chip can be improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the prior art of the present application, the drawings used in the description of the embodiments or the prior art will be briefly described below.

Fig. 1 is a schematic structural diagram of a qubit constituting a quantum chip in the related art;

fig. 2 is a schematic structural diagram of a lumped control line provided in an embodiment of the present application;

FIG. 3 is a schematic diagram of a coupler in the lumped control line of FIG. 2;

fig. 4 shows a schematic structural diagram of a quantum chip in an embodiment of the present application.

Icon: 100-lumped control lines; 101-a control circuit; 102-a coupler; 201-bending section; 202-a non-bending section; 203-a coupling part; 301-open end; 302-ground; 400-qubit; 401 — tunable coupler.

Detailed Description

Qubit 400 is a basic computational unit that is distinguished from classical bits. It is essentially a two-level system that follows the laws of quantum mechanics, and therefore can be in |0>, |1>, or any superposition of the two, with great potential for high-speed computation.

Presently, various physical architectures have been verified to implement qubit 400. Physical implementations of qubit 400 include superconducting systems, semiconductor quantum dot systems, ion traps, diamond vacancies, topological quanta, photons, etc., depending on the physical system employed for construction. Among them, the superconducting system is the fastest and best one of the solid quantum computing implementation methods.

A typical qubit 400 based on a superconducting regime has the structure shown in fig. 1. Qubit 400 has a configuration that may be referred to as a transport (Transmons). As shown in fig. 1, qubit 400 may be implemented using a single capacitive and superconducting quantum interference device (referred to as a "squid") to ground. One end of the superconducting quantum interference device is grounded, and the other end of the superconducting quantum interference device is connected with the capacitor. The magnitude of the equivalent critical current Ic of squid is adjusted by the external magnetic field Φ e, so that the qubit 400 can be controlled on the basis thereof, for example, by adjusting squid with the Z control line.

Wherein squid is a superconducting loop with a josephson junction. Josephson junctions are weak connecting structures for superconductors. The Josephson Junction (JJ) in the example consists of two superconductors with a thin insulating layer in between, which thus has a three-layer structure. The insulating layer in the junction is thin, allowing the cooper pair to exhibit a quantum tunneling effect, and thus the josephson junction exhibits a behavior different from that exhibited by a general superconductor and insulator.

For such superconductor-insulator-superconductor (SIS) josephson junctions, the maximum allowable supercurrent is described as the critical current. When the current through the josephson junction is less than the critical current, the junction exhibits different behavior than a general device; when the current is larger than the critical current, the junction exhibits a behavior similar to a general resistance. In fig. 1, a superconducting quantum interference device squid is a superconducting loop formed by two josephson junctions in parallel, the critical current of which allows tuning by an applied external magnetic field.

The capacitance is typically chosen to be cross-shaped parallel plate/cross-shaped capacitive plate. Which has a designed value of capacitance to ground and on the basis of which there is a gap between the cross-shaped capacitive plate Cq and the ground plane (GND), see fig. 1. The cross-shaped capacitor plate Cq is surrounded by its surrounding ground plane GND. One end of the superconducting quantum interference device squid is connected to the cross-shaped capacitive plate Cq, while the other end thereof is connected to the ground plane (GND).

Referring to the orientation shown in FIG. 1, the first end (vertically down) of the cross-shaped capacitive plate Cq is typically used to connect a superconducting quantum interference device squid, while the second end (vertically up) is used to couple with the read resonator. For example, a space for arranging a pulse control signal line (also referred to as an XY signal line) and a magnetic flux control signal line (also referred to as a Z signal line) is reserved near the first end of the cross-shaped capacitor plate Cq. The other two ends (two ends in the horizontal direction) of the cross-shaped capacitor plate Cq can be used for coupling with the adjacent qubits 400, so that a one-dimensional bit chain can be formed.

The pulse control signal line is a transmission line for applying a qubit 400 transition excitation pulse signal to the qubit 400 of a specific frequency, and the magnetic flux control signal line is a signal line for transmitting a drive signal to generate a magnetic field coupled to the qubit 400 to thereby realize frequency control of the qubit 400.

As shown in fig. 1, a qubit 400 is disclosed and a pulse modulation control line, i.e., an XY control line, is provided. Therefore, when there are a plurality of qubits 400 in the chiplet, the number of XY control lines that need to be arranged is also large. And the control line needs to be connected with a generating source of the control signal through a pin. Therefore, in the case of multiple bits, the number of pins is also large. This results in a chip that is difficult to scale down and difficult to route.

Therefore, if the number of pins required for the XY control line can be reduced in a multi-bit quantum chip, the manufacturing efficiency of the chip will be improved, the manufacturing difficulty will be reduced, and the size of the chip will be controlled. Based on this need, the inventors have studied to propose a very promising solution.

It is considered that in the control mode of qubit 400, the XY control line transmits a high frequency signal. Therefore, for a multi-bit quantum chip, when determining the branch line (corresponding to each qubit 400) frequency, the foregoing solution can achieve the effect of splitting multiple mixed signals by using a bus-based filter.

In other words, the XY control lines originally configured independently for each qubit 400 are adjusted to one bus to couple filters for each qubit 400. One of the buses is used to transmit the mixed signal synthesized by the control signals corresponding to each qubit 400. Since the hybrid signal is unable to achieve the desired control effect for any single qubit 400, the hybrid signal is divided by the corresponding filter into the control signals required for the respective qubit 400.

Based on this recognition, in the example of the present application, the inventors propose a lumped control line 100 with a plurality of independent coupling units. The lumped control line 100 can significantly reduce the number of pins required to be equipped, so as to reserve more wiring space for various components in the chip, thereby reducing the wiring difficulty and facilitating the reduction of the size of the chip.

In general, the lumped control line 100 comprises a control circuit 101 and a coupler 102. The lumped control line 100 has a plurality of couplers 102 therein, e.g., at least two, corresponding to a multi-bit quantum chip. The control circuit 101 may be used as the bus, and the coupler 102 may be used as the filter.

In one example, the lumped control line 100 has one or more (e.g., at least two) coupling units. And the coupling unit is constituted by coupling areas corresponding to the coupler 102 and the control circuit 101. The control circuit 101 has an extended track and accordingly all coupling units are arranged at intervals along the extended track. Each coupler 102 therein has a first end and a second end, and the first end of the coupling unit is coupled with the control circuit 101 and the second end of the coupling unit is configured to be coupled with a qubit 400.

In another example, the lumped control line 100 comprises a control circuit 101 and at least two couplers 102. Fig. 2 shows an example with four couplers 102.

Wherein the control circuit 101 has an extended track and thus the control circuit 101 defines at least two coupling areas spaced along the extended track. The respective coupling zones are defined at any selectable distance. For example, a distance between two adjacent coupling regions is defined as D, and thus, in some examples, the distances are the same, or some distances are the same, or all distances are different. The distance D may be measured along the extended track of the control circuit 101.

Both ends of the coupler 102 are used for coupling with the coupling regions of the qubit 400 and the control circuit 101, respectively. The plurality/at least two couplers 102 are independently configured at a distance from each other. I.e., the various couplers 102 are not in physical contact with each other. Since couplers 102 are matched to qubits 400, the distance between couplers 102 is largely determined by the relationship and manner in which qubits 400 are matched.

In an example, coupler 102, qubit 400, and coupling region have a one-to-one correspondence, such as the following: one coupler 102 corresponds to one qubit 400 and one coupling region and different couplers 102 correspond to different qubits 400 and different coupling regions. I.e., one coupler 102, one qubit 400, and one coupling region, can be considered to constitute a set of coupling structures. Thus, there are a corresponding, e.g., equal, number of coupling structures in the lumped control line 100 as there are qubits 400.

Further, in larger superconducting quantum chip systems, the lumped control line 100 in the example is applied. Thus, from the scale of the superconducting qubit system, there are a plurality of superconducting qubits 400 therein, and various control lines corresponding to the qubits 400; and the couplers 102, qubits 400, and coupling regions provided therein may not be in a one-to-one correspondence in quantity.

The control circuit 101 in the lumped control line 100 may be configured in various suitable configurations, for example, adjusted according to the layout of various components in the chip. In some examples, the control circuit 101 may be a linear structure, or it may be a curved structure. Alternatively, the control circuit can be divided into different configurations, i.e. some sections are linear and others are curved. As mentioned in the foregoing, the control line is provided to transmit microwave signals, and therefore it is generally constructed in the manner of a transmission line. For example, the control circuit 101 is a coplanar waveguide transmission line, such as an aluminum coplanar waveguide transmission line.

Similarly, coupler 102 may also be configured as a coplanar waveguide resonant cavity. For example in fig. 2, coupler 102 is a coplanar waveguide and has two ends; the two ends are respectively a ground end 302 and an open end 301. Illustratively, coupler 102 is a half-wavelength resonator. For example, half a wavelength of one-half the wavelength of the frequency of the microwave control signal of qubit 400 coupled in correspondence with coupler 102.

In other words, the length of coupler 102 corresponds to the frequency of qubit 400 corresponding thereto. And corresponding to this, when the frequencies of the respective bits in the chip are the same, the lengths of the respective couplers 102 in the form of coplanar waveguide resonators are also the same. When the frequencies of different qubits 400 are different, the lengths of the corresponding couplers 102 are also different. It will be appreciated that the sections are the same length in all couplers 102, and different in length. Illustratively, each coupler 102 of all the couplers 102 has a different length, and thus the original microwave signal fed by the control circuit 101 may be filtered by the couplers 102 to form a target microwave signal having a matching characteristic with the corresponding coupler 102.

Based on the requirements for controlling chip size, one may attempt to compress the space on the chip surface occupied by coupler 102. For example, referring to fig. 3, the coplanar waveguide resonant cavity is subjected to a bending process, and thus it can be seen that coupler 102 may have a meander-like structure. The meander can be located at various locations of coupler 102, for example, it can be entirely curved, or it can be partially curved.

In one example, the serpentine shape is located between the two ends of the coupler 102. For the example where coupler 102 has a ground end 302 and an open end 301, then the meander may be at ground end 302 and open end 301. Further, when the length of the coupler 102 is relatively large, the bent section in the coupler 102 may be configured in plural in order to control the size of the chip. When there are a plurality of curved segments, the segments may be arranged in the same curved configuration. Alternatively, the individual curved segments are spaced apart. For example, the coupler 102 has at least one non-bent segment 202 (or straight segment) and a plurality of bent segments 201 between the ground end 302 and the open end 301, and adjacent bent segments 201 are connected by the non-bent segment 202.

Since both ends of the coupler 102 are coupled to the control line and the qubit 400, respectively. It is therefore conceivable to make the corresponding coupling section 203 of the coupler 102 have a different configuration for different coupling partners. Illustratively, the coupler 102 has a coupling portion 203, and the coupling portion 203 extends parallel to the control circuit 101, and the ground 302 is located at the coupling portion 203. That is, the coupler 102 and the control line of the straight type are coupled in a parallel line manner. Alternatively, qubit 400 and coupler 102 may be coupled in a vertical-horizontal arrangement.

As an example of the application of the lumped control line 100, the inventor also proposed a quantum chip in the present application.

The qubit chip includes a plurality of qubits 400 and a lumped control line 100. There are four qubits 400 in the example and four couplers 102 configured in a one-to-one correspondence therewith. Both ends of each coupler 102 in the lumped control line 100 are coupled to the qubit 400 and the control circuit 101, respectively. In fig. 4, a qubit 400 consisting of a cross-capacitor and a superconducting quantum interferometer is disclosed, a quantum chip in a configuration cooperating with the lumped control line 100; other components in the quantum chip, such as read lines, are omitted for illustration.

In different examples, the individual bits in the quantum chip may have different associations. For example, the bits are coupled with each other (coupled two by two in sequence), and may be directly coupled or indirectly coupled. Coupling modes between qubits 400 are long-range coupling and local coupling; more specifically, the coupling method between qubits 400 is capacitive coupling or inductive coupling, for example. In other examples, qubits 400 may be associated with each other by way of adjustable coupling. The adjustable coupling fingers can adjust the coupling strength between qubits 400. The adjustable coupling is realized by using an adjustable coupler 401, for example. Tunable coupler 401 includes, but is not limited to, being constructed in the manner of qubit 400, and thus may be referred to as a coupled qubit 400, and is frequency tunable. For the sake of clarity, qubits 400 may be regarded as computational qubits 400, and thus coupling strength adjustable coupling between adjacent computational qubits 400 via coupling qubits 400 is possible.

In addition, all qubits 400 in the quantum chip may be selected from various suitable arrangements, layouts and architectures. For example, some or all of the qubits 400 may be arranged in a one-dimensional chain, or all of the qubits 400 may be arranged in a two-dimensional array, or all of the qubits 400 may be in a network-like structure.

In the above example, the quantum chip to which the lumped control line 100 is applied may be used in a planar chip, and as an example of a non-planar chip, it may be configured as a flip chip. Accordingly, the components in the chip can be configured to be distributed in different spaces according to different requirements. For example, lumped control line 100 is disposed coplanar with qubit 400, control circuit 101 is disposed coplanar with qubit 400, and so on.

The present inventors have now fully described the structure of the lumped control line 100 and the quantum chip in the present example. The structure and advantages of which are clearly disclosed in the foregoing. Fabrication of the exemplary aspects of the present application will be described to facilitate those skilled in the art in practicing the claimed subject matter. The preparation method can be considered as follows:

on a surface such as a silicon or sapphire substrate, one or more materials, such as superconductors, dielectrics and/or metals, are deposited by suitable methods to form one or more thin films. The method of making these films depends primarily on the materials selected. Illustratively, the materials are selected to be deposited by deposition processes including, but not limited to, chemical vapor deposition, physical vapor deposition (e.g., evaporation or sputtering), or epitaxial techniques, among others.

Further, in order to obtain various desired shapes of components, it may be necessary to remove portions of the material as required, i.e. to perform patterning of the thin film, or even the substrate, for example, the material used to construct each circuit component in the present application may be patterned using known exposure (lithographic) means (e.g. photolithography or electron beam exposure). Thus, in some embodiments of the present application, the quantum chips described may remove portions, or even a majority, of one or more materials during the course of a fabrication process during a step of the fabrication process. Similar to the foregoing, depending on the material to be removed, the removal process described may include, for example, a wet etch technique, a dry etch technique, lift-off, or a combination of one or more of the foregoing.

In combination with the above, in the present application, the inventor proposes a scheme, and realizes reduction of the number of pins and corresponding leads in the quantum chip, thereby reducing the wiring difficulty of the multi-bit chip, reducing the size of the quantum chip, and improving the packaging efficiency of the quantum chip.

The embodiments described above with reference to the drawings are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the foregoing description explains the embodiments of the present application in detail with reference to the drawings. However, it will be appreciated by those of ordinary skill in the art that in the various embodiments of the present application, numerous technical details are set forth in order to provide a better understanding of the present application. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments. The division of the examples is for convenience of description, and should not constitute any limitation to the specific implementation manner of the present application, and the embodiments may be mutually incorporated and referred to each other without contradiction.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein.

Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The construction, features and functions of the present application are described in detail in the embodiments illustrated in the drawings, which are only preferred embodiments of the present application, but the present application is not limited by the drawings, and all equivalent embodiments that can be modified or changed according to the idea of the present application are within the scope of the present application without departing from the spirit of the present application.

Claims (12)

1. A lumped control line, comprising:

a control circuit having an extended trace, the control circuit defining coupling regions distributed along the extended trace; and

and a coupler, and one end of the coupler is coupled with the coupling region of the control circuit, and the other end of the coupler is configured to be coupled with the qubit.

2. The lumped control line of claim 1, wherein the number of coupling regions is at least two, all coupling regions being spaced along the extended trace of the control circuit;

the number of the couplers is at least two, and each coupler is independently configured at intervals;

the coupler, qubit and coupling region have the following correspondence:

one coupler corresponds to one qubit and one coupling region and different couplers correspond to different qubits and different coupling regions.

3. The lumped control line of claim 1, wherein the control circuit is a linear structure;

and/or the control circuit is a coplanar waveguide transmission line;

and/or the coupler is a coplanar waveguide resonant cavity.

4. The lumped control line of claim 1, wherein the coupler is a coplanar waveguide having two ends and being a ground end and an open end, respectively.

5. The lumped control line of claim 4, wherein the coupler is a half-wavelength resonator;

and/or the number of the couplers is multiple, and the length of each coupler is different, so that the original microwave signal fed by the control circuit forms a target microwave signal matched with the corresponding coupler after being filtered by the couplers.

6. The lumped control line of claim 4 or 5, wherein the coupler has a coupling portion extending parallel to the control circuit, the ground terminal being located at the coupling portion.

7. The lumped control line of claim 6, wherein the coupler meanders between a coupling and an open end.

8. The lumped control line of claim 7, wherein the coupler has at least one non-bent segment and a plurality of bent segments between a coupled portion and an open end, and adjacent bent segments are connected by the non-bent segment.

9. A quantum chip, comprising:

a plurality of qubits; and

the lumped control line according to any one of claims 1 to 8;

the coupler in the lumped control line is coupled to a qubit.

10. The quantum chip of claim 9, wherein some or all of the qubits are in one-dimensional chain arrangement and coupled two-by-two in sequence;

and/or the lumped control line is arranged in a coplanar manner with the quantum bit;

and/or the control circuit is arranged coplanar with the qubit.

11. The quantum chip of claim 9, wherein the qubits are computational qubits, and wherein adjacent computational qubits are coupled by coupling qubits.

12. The quantum chip of claim 11, wherein the frequency of the coupled qubits is tunable.

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