Control and readout topology for spin qubits

Abstract

An integrated system (201) for quantum computing is provided, comprising at least: at least one semiconductor spin qubit (210); a feed line (240) configured to function as an electronic spin resonant (ESR) antenna for control of the at least one qubit; at least one resonator (220_j); and a ground plane (250) shared by the feed line and the at least one resonator. The at least one resonator is capacitively coupled to the feed line and configured for readout of the at least one qubit via the feed line. The feed line and the at least one resonator are arranged in adjacent layers separated at least by a dielectric. A corresponding method for performing quantum computing using such an integrated system is also provided.

Description

Technical Field

[0001] This disclosure generally relates to the field of quantum computing. More specifically, this disclosure relates to the control and readout of systems using one or more semiconductor spin qubits. Background Technology

[0002] Over the past decade, the field of quantum computing has expanded with the demonstration of several small-scale quantum computer prototypes. Semiconductor spin qubits are one of the candidates for realizing quantum processors, offering a compact form factor and a long qubit stabilization time (e.g., in terms of relaxation and coherence). These spin qubits are also interesting because they can be fabricated using similar techniques to those already employed in the microelectronics industry, and it is expected that in the coming years, existing prototypes will be able to scale to at least several dozen qubits, ushering in the so-called noisy medium-scale quantum (NISQ) era of quantum computing.

[0003] However, it is known that the operation (including readout and control) of semiconductor spin qubits requires complex radio frequency (RF) technology and design. As the number of semiconductor spin qubits on the same chip is expected to increase, the design of qubit chip wiring fan-outs and peripherals (including microwave sources), filtering at different cooling stages, and printed circuit boards (PCBs) will become increasingly complex. Therefore, improved system designs are needed, with, for example, a reduced number of RF lines interacting with the quantum chip to simplify design requirements, and similarly, a reduced footprint for peripherals. Summary of the Invention

[0004] According to a first aspect of this disclosure, an integrated system for quantum computing is provided. The system includes at least one semiconductor spin qubit. The system includes a feed line configured to function as an electron spin resonance (ESR) antenna for control of the at least one qubit. The system also includes at least one resonator and a ground plane shared by the feed line and the at least one resonator. In this system, the at least one resonator is capacitively coupled to the feed line and configured for readout of the at least one qubit via the feed line. The feed line and the at least one resonator are arranged in adjacent layers separated at least by a dielectric.

[0005] Compared to conventional systems, the system described above offers at least three advantages.

[0006] A first advantage is achieved by providing a feed line and at least one resonator for qubit control in different layers separated by a dielectric. In conventional systems, the feed line and resonator are placed in the same plane, and capacitive coupling between them is achieved by having the feed line and resonator travel parallel (along an “overlap length”) and separated by a finite distance, at least in a portion of the plane. Capacitive coupling can be increased by reducing the finite spacing between the feed line and resonator and / or by increasing the “overlap length” in which the feed line and resonator travel parallel to each other in a portion of the plane. In contrast, in the system according to this disclosure and the first aspect, the feed line and at least one resonator overlap instead in terms of area. Thus, while still achieving similar capacitive coupling, the “overlap length” can be reduced, and the total area of ​​the system (i.e., the occupied area) can therefore be reduced. For example, a sufficient “overlap length” in the system according to the first aspect can be on the order of tens of micrometers, compared to hundreds of micrometers (μm) in conventional systems.

[0007] A second advantage is also achieved by providing the feed line and at least one resonator in different planes, at least separated by a dielectric. This allows the feed line and at least one resonator to be placed much closer to each other (i.e., at a distance corresponding to, for example, the thickness of the dielectric, such as tens of nanometers). In conventional systems, the feed line and resonator are, for example, created in the same plane, with a separation distance between them on the order of a few micrometers. Reducing the distance between the feed line and the resonator can thereby provide stronger capacitive coupling and improved sensitivity to the quantum spin state of at least one qubit.

[0008] The third advantage is achieved by having a shared ground plane between the feed line and at least one resonator, and at least one resonator being configured to read out at least one qubit via the feed line (using, for example, a reflection measurement technique). In other words, the feed line can be used for both control and readout, and using a single (RF) feed line for both qubit control and readout reduces the number of RF lines required on the chip, for example, by a factor of two. Furthermore, sharing a ground plane between the feed line and the resonator also reduces the overall system size, as a separate ground plane for each resonator is no longer needed. For example, the ground plane may “belong” to the feed line (i.e., be on the same layer as the feed line) but is also used by the resonator. These features can lead to reduced complexity, including a further reduction in footprint, compared to conventional systems (where, for example, separate RF feed lines are used for qubit control and readout). The reduction in the number of RF feed lines required for qubit control and readout can also, for example, simplify the design of peripheral devices (including, for example, PCBs, RF filters, and coaxial cables).

[0009] In one or more embodiments, the thickness of the dielectric may be between 20 nm and 40 nm. This thickness may correspond to the distance between the feed line and at least one resonator (in a direction perpendicular to the plane). In one or more embodiments, the system may also include radio frequency (RF) input / output devices connected to the feed line.

[0010] In one or more embodiments, the RF input / output device may include a combined RF input / output port connected to the same end of the feed. Having only a single RF input / output port can further reduce the complexity and footprint of the system. Furthermore, if there is only a single RF input / output port at one end of the feed, it is conceivable to place one or more qubits at the other end of the feed. By doing so, the location of one or more qubits can coincide with the node of the RF electric field, such that when the RF electric field is zero or at least minimal, the one or more qubits can be subjected to only the RF magnetic field. The absence of the RF electric field at one or more qubits can, for example, help prevent stability degradation.

[0011] In one or more embodiments, the RF input / output device may include an RF input port connected to one end of the feed line and an RF output port connected to different ends of the feed line. If one or more qubits are placed in the middle of, for example, a resonator, reflection (e.g., S...) occurs. 11 ) and transmission (e.g., S) 12 The coefficient can be used to measure one or more resonators, which can, for example, provide greater measurement flexibility and calibration.

[0012] In one or more embodiments, the impedance of at least one resonator may be at least 1 kiloohm (kΩ). More generally, it is envisioned that having a high-impedance resonator can help improve the readout signal. Here, "high impedance" may, for example, correspond to an impedance much greater than 50 ohms.

[0013] In one or more embodiments, the Q factor of at least one resonator may be in the range of 1,000 to 10,000.

[0014] In one or more embodiments, at least one qubit may include a plurality of semiconductor spin qubits. The at least one resonator may include a plurality of resonators, and each resonator may have a different resonant frequency for readout of the plurality of qubits using frequency division multiplexing. As described earlier herein, placing the feed line and resonators in separate planes allows for a reduction in system footprint and allows for coupling of more resonators within the same footprint. Furthermore, since the required "overlap length" is smaller than in conventional systems (as described above), the length of the resonators can be reduced, and crosstalk between resonators can therefore be reduced, which can also help allow for an increase in the number of coupled resonators and qubits.

[0015] In one or more embodiments, the at least one quantum dot can be used to implement the at least one qubit. Generally, a “qubit” as used herein includes, for example, at least one electron and its spin state, and the quantum dot can provide a suitable container for such an electron. Other such “containers” are also contemplated, such as, for example, donor-based qubit containers, in which donor atoms are implanted, for example, into silicon, and the spin of additional electrons in the donor acts as qubits. Here, “qubit” may refer only to the spin state of the electron itself, or to the spin state plus the structure used to confine the electron carrying the spin (e.g., a quantum dot). Unless explicitly stated otherwise, the term “qubit” will be used herein to refer to both the spin state itself and the container (e.g., a quantum dot) for the electron carrying the spin state.

[0016] According to a second aspect of this disclosure, a method for performing quantum computing (e.g., using an integrated system according to any embodiment of the first aspect) is also provided. The method includes both controlling and reading out the state of at least one semiconductor spin qubit using the same (single) feeder. In one or more embodiments, the system has multiple qubits and a resonator (as described above), and the method may subsequently include using the feeder and frequency division multiplexing to both control and read out the states of the multiple semiconductor spin qubits. Any advantages or details specified for the system according to the first aspect also apply to the corresponding method according to the second aspect, and additional objectives and advantages of various embodiments of this disclosure will be described below by way of illustrative examples. Attached Figure Description

[0017] Examples of conventional systems and exemplary embodiments according to this disclosure will now be described with reference to the accompanying drawings, in which:

[0018] Figure 1 A conventional system used for quantum computing is illustrated schematically;

[0019] Figure 2a An example embodiment of an integrated system for quantum computing according to the present disclosure is illustrated schematically;

[0020] Figure 2b The illustration explains the basis Figure 2a Example geometry of the system;

[0021] Figure 2c An illustrative explanation Figure 2b The system's cross-section, and

[0022] Figure 2d The illustration explains the basis Figure 2a Another example of the geometry of the system.

[0023] In the accompanying drawings, unless otherwise stated, the same reference numerals will be used for the same elements. Unless explicitly stated to the contrary, the drawings only show those elements necessary to illustrate the exemplary embodiments, while other elements may be omitted or only implied for clarity. As shown in the various drawings, the dimensions of elements and regions are exaggerated for illustrative purposes; therefore, the dimensions of layers and regions are provided to illustrate the general structure of the embodiments. Detailed Implementation

[0024] Spin qubits, based on quantum dots in silicon, for example, can be used to perform quantum computing operations. The state of a qubit can be encoded in the spin state (i.e., "up" or "down") of an electron in the quantum dot, for example, relative to an externally applied static magnetic field. By being able to detect and manipulate such spin states, qubits can be read out and controlled according to the requirements of various quantum computing algorithms. The following will refer to... Figure 1 Further details are given regarding general methods for controlling and reading out such qubits. An advantage of silicon-based spin qubits is that they can be fabricated using existing techniques for manufacturing, for example, conventional transistors. The size of qubits can be very compact and spans, for example, tens of nanometers. Qubits can be tuned using one or more gate electrodes and exhibit decreasing stability in terms of relaxation and coherence times. Silicon-based spin qubits can also operate at higher temperatures (e.g., at a single Kelvin K), while other qubits typically require at most a few millikelvin (mK) to function properly.

[0025] Various techniques have been developed for reading out qubits, including, for example, the use of various charge sensors (such as single-electron transistors and / or quantum dot contacts). These charge sensors are typically compact in design and can operate at relatively low frequencies. However, they can be geometrically complex and often require several DC lines attached to the qubit side. Other techniques use, for example, gate reflectometers, where the geometry on the qubit side is less complex, and the qubit can operate at higher temperatures. However, such techniques do have other drawbacks, such as the need for radio frequency (RF) signals and therefore more complex external circuitry (e.g., PCBs, coaxial cables, etc.), especially when implementing and using multiple qubits.

[0026] Various techniques for controlling qubits have also been developed, including, for example, techniques based on magnetic resonance (e.g., electron spin resonance, ESR) via transmission lines. These techniques allow for smaller qubit dephase, but can typically be slow. Other qubit control techniques include those based on electric dipole spin resonance (EDSR) with micromagnets; these are faster, but often result in larger qubit dephase.

[0027] To enable one qubit to interact with another, developed techniques include swap interactions (which result in fewer qubits dephasing but require larger or very close quantum dot spacing) and resonators (which allow quantum dots to be further apart but may produce stronger dephasing).

[0028] Generally, conventional qubit systems typically rely on complex external circuitry to read out and control qubits, through various combinations of the aforementioned techniques. A particular combination is based on a reflector for reading out one or more qubits and an ESR for controlling those qubits. Therefore, various microwave sources, filters at different cooling stages, and a PCB capable of transmitting microwave signals to the chip housing the qubits are usually required, along with multiple input and output ports / interfaces for such signals. Furthermore, the footprint of a qubit chip is typically quite large.

[0029] Now refer to Figure 1 Examples of conventional systems used for quantum computing are described in more detail.

[0030] Figure 1A conventional system 100 is schematically illustrated, including qubits 110 (or an arrangement of multiple qubits). To read out the state of qubit 110, system 100 includes a resonator 120, which can provide various RF input / output signals 130 to / from the resonator 120. Qubit 110 is also equipped with various DC and low-frequency (e.g., sub-GHz) signals 132 for defining, for example, one or more quantum dots within the qubit for confining electrons carrying quantum spin states. Qubit 110 may include, for example, a barrier gate for defining the quantum dots, and a point-specific gate, which can be used to move energy levels up and down within the point. Readout of qubit 110 can be performed, for example, by loading a first electron with a specific spin (e.g., spin down) onto a first quantum dot within qubit 110, and a second electron (carrying the spin state to be determined) can be located (using various gates) onto a nearby second quantum dot. Due to the Pauli exclusion principle, the probability of the second electron tunneling from the second point to the first point will depend on the spin state of the second electron. For example, if the first electron on the first quantum dot has a spin-down, then if the second electron has the opposite spin state (i.e., spin-up), the probability of the second electron tunneling from the second quantum dot to the first quantum dot is higher; if the spin state of the second electron is the same as that of the first electron (i.e., spin-down), the probability is lower or zero. If tunneling occurs, the resonant frequency of resonator 120 will change, and this can be detected via input / output signal 130. This technique, known as a "reflectometer," can therefore be used to determine the spin state of electrons in system 100 (and thus the state of the qubit). This can be achieved, for example, by measuring the amplitude and phase of the signal reflected at qubit 110. System 100 can be, for example, a single-port system, where input / output signals 130 to / from the resonator are provided at the same interface, and where qubit 110 is arranged at the end of resonator 120. Conversely, system 100 can also be a two-port system, with separate input and output ports for each input / output signal 130, wherein a resonator 120 is connected between these two ports, and wherein qubits 110 are arranged in a side-branch manner to the resonator 120. For a conventional system to function as intended, the resonator 120 is typically sized such that its width is tens of nanometers (e.g., about 50-100 nanometers), its length is on the order of millimeters (e.g., about 1 millimeter), and its distance from one or more ground planes is on the order of micrometers (e.g., about 1 μm). If system 100 includes more than one qubit, multiple resonators can be provided, each with a slightly different length, and each resonator is connected to one qubit. Since the resonant frequency of each resonator will depend on its length, the state of different qubits can be determined separately by adjusting the frequency of the input signal accordingly, so that each resonator is excited individually.As an example, the length difference between subsequent resonators can be, for example, on the order of 10%.

[0031] In system 100, the resonator is typically arranged without any physical connection to an external circuit system. Instead, one or more feed lines are capacitively coupled to the resonator, with the feed lines lying in the same plane as the resonator. As described earlier, the strength of the capacitive coupling between the coplanar feed lines and the resonator is determined by the “overlap length” between the resonator and the feed lines (i.e., the distance the resonator travels parallel to the feed lines at a finite separation distance). The required overlap length is typically on the order of several hundred micrometers (e.g., about 500 μm). The resonator is typically created by removing a portion of the ground plane associated with the feed line, and the spacing between the feed line and the ground plane (and therefore the finite distance between the feed line and the resonator) is typically on the order of at least several micrometers.

[0032] like Figure 1 As shown, to control the qubit 110, the system 100 also includes a control feed line 140. The feed line 140 can be, for example, an electron spin resonance (ESR) antenna equipped with various RF input / output signals 134, and the feed line 140 can be sufficiently close to the qubit 110 such that the signals 134 can be used to control the state of the qubit 110. For example, spin resonance can be used, where a static magnetic field is first applied perpendicular to the interface of the qubit, forming a quantum dot containing electrons with qubit spin states at the interface, thereby generating a Zeeman energy split between electrons with up-spin or down-spin, where the energy split is proportional to the strength of the applied static magnetic field. Simultaneously, the electron spin will revolve around the applied static magnetic field, and its Larmor frequency is also proportional to the strength of the applied static magnetic field. However, in a reference frame rotating at this frequency, the electron spin will remain stationary.

[0033] By coupling feed line 140 (via signal 134) to an external microwave (AC) source, an AC magnetic field can be generated in a direction perpendicular to the applied static magnetic field. If the AC magnetic field has a field frequency that matches the Zeeman energy split, the electron spin can be forced to rotate in a controlled manner in a rotating reference frame, where, for example, the combination of the duration and amplitude of the applied AC magnetic field pulse (i.e., the region defined by the pulse plotted as amplitude versus time) will determine how far the spin has rotated in that rotating reference frame. This technique, known as (pulsed) “electron spin resonance” (ESR), can therefore be used to control spin states and qubits on demand.

[0034] In system 100, feed line 140 is also equipped with its own ground plane (not shown). Furthermore, if more than one resonator and more than one qubit are used, a separate feed line can be provided to each resonator for qubit readout. Alternatively, in other conventional alternatives, a single feed line can be capacitively coupled to multiple resonators, thereby allowing qubit readout using a single feed line. In any conventional case, the aforementioned resonator size requirements still apply to such conventional systems because the feed line and resonator are located in the same plane.

[0035] As described herein, this disclosure improves conventional systems by providing an integrated system design with a reduced footprint, and in addition to facilitating the use of more silicon-based qubits, the reduced number of external RF interfaces to the chip allows for simplified design of external peripheral devices.

[0036] Now refer to Figures 2a to 2d Various embodiments of such integrated systems for quantum computing according to this disclosure are described.

[0037] Figure 2a An example embodiment of system 200 is illustrated schematically, including a qubit arrangement 210 containing a plurality of qubits (here assumed to be a total of N qubits). As will be described in more detail below, a qubit may be defined, for example, by a plurality of quantum dots formed within the qubit arrangement 210, and the qubit arrangement 210 receives a plurality of DC and low-frequency (e.g., sub-GHz) signals 232 for defining and controlling each qubit within the arrangement 210 via, for example, a plurality of gates.

[0038] System 200 includes multiple resonators 220_1-N, which are used to read out the qubits in the qubit arrangement 210 using a reflectometer. As discussed earlier herein, the resonators 220_1-N can have different lengths, such that they each have different resonant frequencies, and that the qubits can be read out individually. Each resonator 220_1-N is coupled to a corresponding qubit within the qubit arrangement, for example, coupled to a gate above a quantum dot used to confine electrons having qubit spin states.

[0039] System 200 also includes a single feed line 240 serving as an ESR line / antenna for controlling individual qubits using ESR. Feed line 240 is also capacitively coupled to each resonator 220_1-N, and feed line 240 can therefore also be used to measure resonators 220_1-N, and thus for the individual readout of several qubits. Since resonators 220_1-N have different lengths, frequency (frequency division multiplexing) can be used to control and readout multiple qubits using only a single feed line 240. Resonators 220_1-N and feed line 240 are arranged in different adjacent planes separated at least by a dielectric, and a portion 221 of resonator 220_1-N extends below the housing showing feed line 240. As previously described, this allows feed line 240 and resonators 220_1-N to be arranged closer to each other (with a finite separation distance corresponding to, for example, the size of the dielectric), resulting in improved capacitive coupling without increasing the footprint. From another perspective, while reducing the footprint of system 200, the necessary capacitive coupling between feeder 240 and resonator 2201-N can be maintained.

[0040] References to this article Figure 1 In contrast to the conventional system 100 described herein, the system envisioned herein (e.g., 200) uses a single feed line capacitively coupled to one or more resonators for the readout and control of one or more qubits.

[0041] Feeder 240 and resonator 220_1-N also share a common ground plane. Figure 2a (not shown in the diagram), and a set of signals 236 for reading out and controlling the qubits in the qubit arrangement 210 are all provided at the combined RF input / output terminals of the feed line 240 (e.g., at the end of the feed line 240 opposite to the end where the qubit arrangement 210 is located). Therefore, qubit readout and control can be implemented using a reduced number of RF ports.

[0042] Figure 2b A more detailed description based on the reference Figure 2a The geometric layout of an example embodiment of system 201 of system 200 is described. The same principles discussed for system 200 also apply to system 201, and most of the specific details not discussed for system 200 will be described below.

[0043] System 201 includes a feed line with a single-port geometry, wherein an RF signal 236, comprising input and output signals (for both readout and control of the qubits), is provided at a single RF input / output port at the end of feed line 240. Feed line 240 is also associated with a ground plane 250 provided in the same layer as feed line 240. Ground plane 250 is configured such that it can also be shared with a plurality of resonators 220_1-N disposed in a layer below feed line 240 and ground plane 250.

[0044] The qubit arrangement 210 is arranged below the feed line portion 242, and each resonator 220_j is connected to the corresponding qubit in the qubit arrangement 210 at the end not used for coupling to the feed line.

[0045] like Figure 2b As shown, feed line 240 and resonator 220_1-N are defined with specific dimensions. The width of the feed line is w. F The separation distance between the ground plane 250 and the feeder 240 is s. F The overlap length between each resonator 220_1-N and the feed line 240 is l. O Each resonator 220_j (where j is an integer between 1 and N, and N is the total number of resonators, which is also the total number of qubits) has a length l. Rj The resonator travels along a portion of the ground plane to that length. Figure 2b In the diagram, for clarity, the remaining length of each resonator (e.g., traveling between feed line 240 and ground plane 250, and between ground plane 250 and qubit arrangement 210) is shown as having a length l Rj A considerable size. However, in the manufactured system 201, the lengths of these segments (corresponding to the portions of the external resonator at the ground plane 250) are conceived to be greater than l Rj Much smaller, such that in an approximation, the length l Rj This can correspond to almost the entire length of the resonator 220_j. However, in the case of a high-impedance (>>50 ohms) resonator, the width w of the resonator can be envisioned. R (that is, w for resonator 220_j) Rj (This is) much smaller than the 250mm gap between the resonator and the ground plane. R (that is, for resonator 220_j, it is s) Rj In this case, even if a portion of the resonator that does not travel along the ground plane 250 is a few micrometers away from the ground plane 250, this portion of the resonator will still be included in the resonant frequency of the resonator. Therefore, even if the portion of the resonator 220_j not included in l RjThe individual parts are very small, and the entire length of the resonator can be included when each resonator is designed to have a specific resonant frequency. Therefore, the total length of resonator 220_j can be adjusted to achieve sufficient differentiation between signals originating from different qubits. It is also conceivable that the cutouts in ground plane 250 (where the corresponding feed lines travel along ground plane 250) can be tuned to achieve the desired resonant frequency.

[0046] Imagine various DC and low-frequency signals ( Figure 2b (Not shown in the text) is also provided for the qubit arrangement 210, as described earlier in this document.

[0047] Figure 2c The system 201 is shown along Figure 2b The cross section 202 of the dashed line AA includes at least a portion of the cross section of the qubit arrangement 210. Feed line 240 (or at least a portion thereof 242) is disposed in a separate plane adjacent to the plane of each resonator 220_1-N. Each resonator 220_1-N serves as (or is at least connected to) a gate 260_1-N disposed in another layer separated from the layer of feed line 240 by a dielectric 266 (e.g., SiO2). The qubit arrangement also includes barrier gates 262_1-N, which, together with the gates 260_1-N defined by (or at least connected to) the resonators 220_1-N, define a plurality of quantum dots 263_1-N at the interface between the dielectric 266 and the (e.g., silicon) substrate 264. Additional gates and storage devices (e.g., for limiting perpendicularity) are also included. Figure 2c Electrons in the dimensions of the cross-sectional plane shown can completely define the confinement gates of the quantum dots, the storage gates for controlling the entry and exit of electrons from each quantum dot, the corresponding storage, additional 2DEGs, etc., and the like, and can also be included in the quantum bit arrangement, but... Figure 2c Not shown in the diagram. Gates not formed by or connected to resonator 220_1-N may be connected to various DC or low-frequency voltages, such as... Figure 2a The DC and low-frequency signals 232 shown are provided.

[0048] The separation distance between the layers of feeder 240 and resonator 220_1-N is t. OX-R The separation distance between the gate and the interface forming the quantum dot 263_1-N is t. OX The width of quantum dot 263_j is w. D The length of quantum dot 263_j (e.g., in the direction perpendicular to...) Figure 2c In the cross section shown, l is D The spacing between two adjacent quantum dots 263_j is b. D .

[0049] Figure 2d Another example embodiment of system 203 is schematically shown, which includes six resonators 2201-6 coupled to a qubit arrangement 210, which may also include six qubits, for example. Of course, it is conceivable that other numbers of resonators and / or qubits may be used, and system 203 is merely one possible conjectural example. This applies to any system disclosed herein, and as exemplified, also to the references. Figure 2b The system 201 described does not necessarily have to be eight in total, including qubits and / or resonators.

[0050] The features of system 203 (unless otherwise stated) are the same as those described above. However, with reference to this document... Figure 2b Compared to the described system 201, system 203 has a two-port geometry, wherein the input port is arranged at one end of feed line 240 (for receiving RF input signal 237), and the output port is arranged at the other end of feed line 240 (for receiving RF output signal 238). The qubit arrangement 210 is not located at one end of feed line 240, but rather approximately in the middle (and below) of feed line 240. As previously stated, nodes in the RF electric field are not necessarily present at the location of qubit arrangement 210; however, using separate input and output ports at each end of feed line 240 allows for the use of the reflection coefficient (S). 11 ) and transmission coefficient (S 12 ) is used as a parameter to calibrate and operate the readout and control of the qubit arrangement 210 using a single feeder 240.

[0051] Such as about Figure 2b As described in system 201, when determining the resonant frequency of each resonator, the total length l of each resonator is considered. Rj To tune these resonant frequencies so that they are sufficiently different from each other (so that frequency division multiplexing can be used to read out / control qubits), it is envisioned that, for example, the cut width in the ground plane 250 for each resonator can be different, and / or the length of the resonator outside the ground plane 250 can be adjusted accordingly, even with respect to the length l of the portion of resonator 220_j that travels along the ground plane 250 within its dedicated cut in the ground plane 250. Rj In comparison, these lengths are conceived to be very small, as discussed earlier in this article. For example, although in Figure 2d The resonators are shown as symmetrical, for example, the total length of resonator 220_1 does not need to be exactly matched with the total length of resonator 220_6; for example, the total length of resonator 220_2 does not need to be completely matched with the total length of resonator 220_5, and similarly, the total lengths of resonators 220_3 and 220_4 do not need to be completely matched.

[0052] In systems as described herein according to one or more aspects of this disclosure, for example Figure 2b , 2c The various dimensions given in 2D can be, for example, as follows: w F It can be on the order of a few micrometers (e.g., about 4.2 μm); s F It can be on the order of a few micrometers (e.g., about 3 μm); F It can be on the order of millimeters (e.g., approximately 1 mm); O It can be on the order of tens of micrometers (e.g., 40 μm); w Rj It can be on the order of tens of nanometers (e.g., about 50 nm); s Rj It can be on the order of a few micrometers (e.g., about 1 μm); l Rj It can be on the order of fractions of a millimeter to several millimeters (e.g., approximately 0.5–1.1 millimeters); each l Rj The difference may be about 10%; t OX-R It can be on the order of tens of nanometers (e.g., about 20-40 nm, such as 30 nanometers); t OX It can be on the order of a few nanometers (e.g., about 8 nm); w D It can be on the order of tens of nanometers (e.g., about 50 nm); D The dimensions can be on the order of tens of nanometers (e.g., approximately 50 nm), and bD can be on the order of tens of nanometers (e.g., approximately 30 nm). It should be noted that the dimensions given are approximate only, and variations are still possible within the scope of this disclosure. Therefore, the dimensions presented herein should not be considered limiting, but rather as illustrating one of many possible embodiments.

[0053] However, special attention should be paid to, for example, the overlap distance l between the resonator and the feed line. O The overlap distance here is on the order of tens of micrometers, whereas conventional systems without this disclosure typically require an overlap distance on the order of hundreds of micrometers. Similarly, the separation t between the resonator and the feed line... OX-R In this case, the separation is on the order of tens of nanometers, whereas in conventional systems, the separation between the feed line and the resonator (both located in the same plane) is at least several times greater than the separation between the feed line and its ground, i.e., at least several micrometers or even tens of micrometers. According to the system dimensions of this disclosure, because the feed line and the resonator are placed in different layers, increased coupling strength and / or reduced system footprint can be provided; for example, the overlap distance can be reduced while still achieving sufficient coupling strength, and vice versa.

[0054] Here, when the ground plane is referred to as "shared" between the feeder and the resonator, it is envisioned that the same ground plane can be used as the return path for both the feeder and the resonator. If the return current is AC, then even if the ground plane is not in direct physical contact with the feeder or the resonator, the current will be transmitted to the ground plane via capacitive coupling. For the resonator, such capacitive coupling is envisioned as a partial distribution along, for example, a cut in the ground plane of the resonator. Similar capacitive coupling will occur between the feeder and the ground plane.

[0055] Although Figures 2a to 2d Various embodiments in which the system includes multiple qubits have been explained, but it is also conceivable that the system could contain only a single qubit. Even for a single qubit, there are advantages to having the feeder and resonator in separate layers, as well as the benefit of reducing the number of required input / output ports (due to the use of the same single feeder for both readout and control of one or more qubits). In a system with only a single qubit, the need for frequency multiplexing can certainly be avoided, at least in the sense of qubit readout. The pulses used for readout and control may still have different frequencies.

[0056] In short, this disclosure provides a system in which a single shared feed line is used for both readout and control of one or more qubits, wherein a ground plane is shared between the feed line and one or more resonators, and wherein the feed line and resonators are located in different planes separated by a dielectric. This allows for the creation of a less complex structure in which the footprint can be reduced while still achieving sufficient capacitive coupling between, for example, the feed line and the resonators, for both readout and control of the qubits, and wherein the number of input / output ports required can be reduced, resulting in further reductions in complexity and footprint.

[0057] Although features and elements may be described above in specific combinations, each feature or element may be used alone without other features and elements, or in various combinations with or without other features and elements.

[0058] Furthermore, other variations of the disclosed embodiments may be understood and implemented by those skilled in the art from a study of the drawings and this disclosure when implementing the claimed invention. The word "comprising" does not exclude other elements, and the indefinite articles "a" or "an" do not exclude a plural.

Claims

1. An integrated system (201) for quantum computing, comprising: At least one semiconductor spin qubit (210); Feed line (240), the feed line being configured to function as an electron spin resonance (ESR) antenna for the control of the at least one qubit, At least one resonator (220_j), and The ground plane (250) shared by the feed line and the at least one resonator The at least one resonator is capacitively coupled to the feed line and configured for readout of the at least one qubit via the feed line, and The feed line and the at least one resonator are arranged in adjacent layers separated by at least a dielectric.

2. The system according to claim 1, characterized in that, The thickness of the dielectric is between 20 nm and 40 nm.

3. The system according to claim 1 or 2, characterized in that, It also includes radio frequency (RF) input / output devices connected to the feeder.

4. The system according to claim 3, characterized in that, The RF input / output device includes a combined RF input / output port connected to the same end of the feeder.

5. The system according to claim 3, characterized in that, The RF input / output device includes an RF input port connected to one end of the feed line and RF output ports connected to different ends of the feed line.

6. The system according to claim 1 or 2, characterized in that, The impedance of the at least one resonator is at least 1 kiloohm.

7. The system according to claim 1 or 2, characterized in that, The Q factor of the at least one resonator is in the range of 1000 to 10000.

8. The system according to claim 1 or 2, characterized in that, The at least one qubit comprises a plurality of semiconductor spin qubits, wherein the at least one resonator comprises a plurality of resonators, and wherein each resonator has a different resonant frequency for readout of the plurality of qubits using frequency division multiplexing.

9. The system according to claim 1 or 2, characterized in that, The at least one quantum bit is implemented using at least one quantum dot.

10. A method of performing quantum computing using an integrated system according to any one of the preceding claims, comprising using the feed line to control and read the state of the at least one semiconductor spin qubit.

11. The method according to claim 10, characterized in that, This includes using the feed line and frequency division multiplexing to control and read out the states of multiple semiconductor spin qubits.

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