In-situ testing apparatus and method for a quantum bit chip

Abstract

The application discloses an in-situ testing device and method for a quantum bit chip, and the device comprises a laser irradiation unit, a testing table, a probe structure and an electrical property detection device; a vacuum cavity is arranged in the testing table, a window and at least two probe interfaces which are in communication with the vacuum cavity are formed in the side wall of the testing table, a sample table is arranged in the vacuum cavity, and the sample table carries the quantum bit chip; the laser irradiation unit is used for generating laser; the probe structure comprises at least two groups of probe arms and probes, the probe arms penetrate through the probe interfaces, the first end of the probe arm is located in the vacuum cavity, the second end of the probe arm is located outside the vacuum cavity, the probe is fixedly installed at the first end of the probe arm and is electrically connected with the probe arm, and the second end of the probe arm is electrically connected with the electrical property detection device. The application can solve the problem that the oxidation layer of the quantum bit chip influences the accuracy of electrical property testing, and effectively improves the efficiency of electrical property testing of the quantum bit chip.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of superconducting quantum computing, and particularly relates to an in-situ testing device and method for a quantum bit chip. BACKGROUND

[0002] The field of superconducting quantum bits based on Josephson junctions is rapidly developing. In order to optimize the interface contact characteristics of the quantum bits, a micro-laser annealing technique is usually used to induce changes in the interface contact of the Josephson junction quantum bits, thereby causing changes in the bit resistance and bit frequency to regulate the performance of the bits. Testing the electrical characteristics, such as the resistance, of the quantum bit chip becomes an effective method to quickly feed back the changes in the characteristics of the quantum bit chip after laser annealing.

[0003] The prior art usually moves the quantum bit chip modified by laser irradiation to a special electrical probe testing table for electrical testing. However, this process exposes the sensitive quantum bit chip to the atmosphere, and oxidation by water and oxygen can cause an ultra-thin oxide layer to form on the outermost surface of the quantum bit chip. This not only brings uncontrollable factors to the function of the quantum bit chip, but also causes the problem of inaccurate probe testing due to the ultra-thin oxide layer existing in the electrical testing. Therefore, it is necessary to use precise micro-force feedback and displacement adjustment components in combination with resistance monitoring modules and processing modules to break the oxide layer, thereby accurately testing the electrical characteristics. The equipment used in this method is usually expensive, and the operation is complex and inconvenient. Moreover, there are problems such as inaccurate testing, complex operation, and long testing time during the testing process.

[0004] Therefore, in view of the above technical problems, it is necessary to provide an in-situ testing device and method for a quantum bit chip. SUMMARY

[0005] The purpose of the present application is to provide an in-situ testing device and method for a quantum bit chip, which can solve the problem of the influence of the oxide layer of the quantum bit chip on the accuracy of the electrical characteristic testing, and effectively improve the efficiency of the electrical characteristic testing of the quantum bit chip.

[0006] In order to achieve the above-mentioned purpose, the technical scheme provided by an embodiment of the present application is as follows:

[0007] An in-situ testing device for a quantum bit chip, the in-situ testing device comprising a laser irradiation unit, a testing table, a probe structure, and an electrical characteristic detection device;

[0008] The testing table is internally provided with a vacuum cavity, the side wall of the testing table is provided with a viewing window and at least two probe interfaces in communication with the vacuum cavity, and the vacuum cavity is provided with a sample stage for carrying the quantum bit chip.

[0009] The laser irradiation unit is used to generate laser, which enters the vacuum cavity from the window and irradiates the quantum bit chip on the sample table;

[0010] The probe structure comprises at least two groups of probe arms and probes, the probe arms pass through the probe interface, the first end of the probe arm is located in the vacuum cavity, the second end is located outside the vacuum cavity, the probe is fixedly installed at the first end of the probe arm and electrically connected with the probe arm, and the second end of the probe arm is electrically connected with the electrical property detection device.

[0011] In one or more embodiments of the present application, the in-situ testing device further comprises a mechanical pump and a molecular pump, the molecular pump is connected with the vacuum cavity, and the mechanical pump is connected with the molecular pump.

[0012] In one or more embodiments of the present application,

[0013] The probe arm further comprises a connecting rod, a bellows, a first connecting piece and a vacuum electrical feedthrough;

[0014] The probe is fixedly installed at the first end of the connecting rod and electrically connected with the connecting rod, the vacuum electrical feedthrough is fixedly installed at the second end of the connecting rod and electrically connected with the connecting rod, part of the connecting rod is located in the vacuum cavity, and part of the connecting rod is nested in the bellows;

[0015] The first end of the bellows is fixedly connected with the first connecting piece, the second end is sealingly connected with the vacuum electrical feedthrough, and the vacuum electrical feedthrough is electrically connected with the electrical property detection device.

[0016] In one or more embodiments of the present application, the probe interface comprises a second connecting piece fixedly connected with the side wall of the test table, and the first connecting piece and the second connecting piece are connected through a fixing piece.

[0017] In one or more embodiments of the present application, the first connecting piece comprises a first butt flange; and / or,

[0018] The second connecting piece comprises a second butt flange.

[0019] In one or more embodiments of the present application, the in-situ testing device further comprises a coaxial shielded cable, which is connected between the vacuum electrical feedthrough and the electrical property detection device.

[0020] In one or more embodiments of the present application, the electrical property detection device comprises a multimeter.

[0021] In one or more embodiments of the present application, the probe has a diameter of 15-20 μm away from one end of the probe arm.

[0022] In one or more embodiments of the present application, the laser irradiation unit comprises a laser and a lens, the lens being arranged between the laser and the window for collimating and focusing the laser.

[0023] Another specific embodiment of the present application provides a technical solution as follows:

[0024] An in-situ testing method for a quantum bit chip, the method comprising:

[0025] Providing an in-situ testing device;

[0026] Placing the quantum bit chip to be tested on the sample table, and contacting one end of the probe with the Josephson junction on the quantum bit chip to be tested;

[0027] Vacuumizing the vacuum cavity to an ultrahigh vacuum state;

[0028] Generating laser by the laser irradiation unit to irradiate the Josephson junction on the quantum bit chip;

[0029] Obtaining the electrical characteristic signal of the Josephson junction of the quantum bit chip by the probe.

[0030] Compared with the prior art, the in-situ testing device and method for a quantum bit chip of the present application can realize laser irradiation operation and electrical testing operation simultaneously by opening a vacuum cavity in the testing table and opening a window and a probe interface on the side wall of the testing table, without the need to transfer the quantum bit chip, thereby realizing in-situ testing, avoiding exposure of the quantum bit chip to the atmosphere, and improving the accuracy and convenience of electrical characteristic measurement.

[0031] By setting the mechanical pump and the molecular pump in communication, and cooperating with the probe structure connected to the vacuum cavity through the butt-welded flange, the vacuum cavity is ensured to be in a closed state, providing an ultrahigh vacuum environment for the quantum bit chip, effectively avoiding oxidation of the quantum bit chip by water and oxygen, and eliminating the influence of the ultrathin oxide layer on quantum bit electrical measurement from the root.

[0032] The present application does not need to construct a complex special probe system, saving material costs and reducing the complexity of operation. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0034] Figure 1A structural schematic diagram of an in-situ testing device for a quantum bit chip in an embodiment of the present application;

[0035] Figure 2 A probe structural schematic diagram of an in-situ testing device for a quantum bit chip in an embodiment of the present application;

[0036] Figure 3a A scanning electron microscope image of a Josephson junction in an embodiment of the present application;

[0037] Figure 3b A scanning electron microscope image of a Josephson junction in an embodiment of the present application;

[0038] Figure 3c A micro-magnification image of a Josephson junction in an embodiment of the present application;

[0039] Figure 3d A transmission electron microscope image of a Josephson junction in an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the person skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should fall within the protection scope of the present application.

[0041] Unless otherwise explicitly indicated, throughout the specification and claims, the term "comprise" or its variants such as "comprises" or "comprising" will be understood to encompass the stated element or components, but not exclude other elements or components.

[0042] In the specification, "coupling" or "connection" or "connection" includes both direct connection and indirect connection. Indirect connection is the connection through an intermediate medium, such as the connection through an electrically conductive medium, which can have parasitic inductance or parasitic capacitance; indirect connection can also include the connection through other active devices or passive devices on the basis of achieving the same or similar functional purposes, such as the connection through circuits or components such as switches, follower circuits, etc. In addition, in the present application, words such as "first", "second" are mainly used to distinguish one technical feature from another technical feature, and do not necessarily require or imply a certain actual relationship, quantity or order between the technical features.

[0043] In the detailed description of this specification, reference is made to the accompanying drawings, which form a part thereof, wherein like reference numerals always denote like parts, and wherein exemplary embodiments are shown by way of example that may be implemented. It should be understood that other embodiments may be utilized, and structural or logical changes may be made, without departing from the scope of this application. Therefore, the following detailed description should not be considered limiting.

[0044] The various operations in the specification may be described sequentially as multiple discrete actions or operations in a manner most conducive to understanding the claimed subject matter. However, the order of description should not be construed as implying that these operations must be sequentially related. Specifically, these operations may not be performed in the order presented. The described operations may be performed in a different order than in the described embodiments. Various additional operations may be performed in additional embodiments and / or the described operations may be omitted.

[0045] For the purposes of this application, the phrase "A and / or B" means (A), (B), or (A and B). For the purposes of this application, the phrase "A, B and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).

[0046] Various components and devices may be referred to or shown in the singular (e.g., “MOS transistor”, “transistor”, “switch”, etc.) in this document, but only for the convenience of discussion, and any element referred to in the singular may include multiple such elements as taught herein.

[0047] The description uses the phrases "in this embodiment," "in other embodiments," or "in some embodiments," each of which may refer to one or more of the same or different embodiments. Furthermore, the terms "comprising," "including," "having," etc., used in relation to embodiments of this application are synonymous.

[0048] like Figure 1 As shown, an embodiment of the present invention provides an in-situ testing device for a quantum bit chip, the in-situ testing device including a laser irradiation unit 20, a test stage 10, a probe structure 30 and an electrical characteristic detection device 40.

[0049] The test stage 10 has a vacuum chamber 11 inside. The side wall of the test stage 10 has a viewing window 12 that communicates with the vacuum chamber 11 and at least two probe interfaces 13. The vacuum chamber 11 has a sample stage 14 inside, which is used to carry the quantum bit chip.

[0050] The laser irradiation unit 20 is used to generate laser light, which enters the vacuum chamber 11 through the viewing window 12 and irradiates the quantum bit chip on the sample stage 14. In one embodiment, the sample stage 14 is positioned directly below the viewing window 12.

[0051] In one embodiment, the wavelength of the laser is 532 nm. After the Josephson junction on the quantum bit chip is irradiated by the laser, the Josephson junction on the quantum bit chip is modified.

[0052] The probe structure 30 includes a probe arm 32 and a probe 31, the probe 31 arm penetrates the probe interface 13, the first end of the probe arm 32 is located in the vacuum cavity 11, the second end is located outside the vacuum cavity 11, the probe 31 is fixedly installed at the first end of the probe arm 32 and is electrically connected with the probe arm 32, and the second end of the probe arm 32 is electrically connected with the electrical property detection device 40. It can be understood that the probe arm 32 is in sealed communication with the probe interface 13. The probe structure 30 includes at least two groups of probe arms 32 and probes 31, that is, the number of probe arms 32 and the number of probes 31 are equal to the number of probe interfaces 13.

[0053] In the preferred embodiment of the present application, two probe interfaces 13 are opened in the side wall of the test table 10, and the two probe interfaces 13 are symmetrically arranged on both sides of the test table 10. Adaptively, the probe structure 30 includes two probe arms 32 and two corresponding probes 31.

[0054] As shown in Figure 1 , the in-situ testing device in one embodiment further includes a mechanical pump 60 and a molecular pump 70, the molecular pump 70 is in sealed connection with the side wall of the test table 10, and the molecular pump 70 is in communication with the vacuum cavity 11, the mechanical pump 60 is in communication with the molecular pump 70, and the mechanical pump 60 and the molecular pump 70 are used to vacuum the inside of the vacuum cavity 11 to an ultrahigh vacuum state. It can be understood that the ultrahigh vacuum (UHV) state refers to the pressure in the vacuum cavity 11 below 10 -9 mBar, that is, the number of molecules per unit volume is 1 / 1000000000000 of the normal atmospheric pressure.

[0055] As shown in Figure 2 , the probe arm 32 includes a connecting rod 321, a bellows 322, a first connecting piece 323 and a vacuum electric feedthrough 324.

[0056] The probe 31 is fixedly installed at the first end of the connecting rod 321 and is electrically connected with the connecting rod 321, the vacuum electric feedthrough 324 is fixedly installed at the second end of the connecting rod 321 and is electrically connected with the connecting rod 321, part of the connecting rod 321 is located in the vacuum cavity 11, and part of the connecting rod 321 is nested in the bellows 322.

[0057] The first end of the bellows 322 is fixedly connected with the first connecting piece 323, the second end is sealingly connected with the vacuum electric feedthrough 324, and the vacuum electric feedthrough 324 is electrically connected with the electrical property detection device 40.

[0058] It is understood that the first end of the connecting rod 321 is the first end of the probe arm 32, and the vacuum electric feeder 324 is the second end of the probe arm 32. Further, in one embodiment, the vacuum electric feeder 324 includes a weld flange structure, thereby achieving a sealed connection with the bellows 322. It is understood that the probe 31 is completely placed inside the vacuum chamber 11.

[0059] The probe interface 13 includes a second connector 131 fixedly connected to the side wall of the test bench 10, and the first connector 323 and the second connector 131 are connected by a fastener. Optionally, the fastener includes a bolt.

[0060] In one embodiment, the first connector 323 includes a first welding flange, and the second connector 131 includes a second welding flange. It is understood that the first and second welding flanges are dimensionally matched, and the sealing connection of the welding flanges ensures that the bellows 322 of the probe arm 32 is connected to the vacuum chamber 11 to an ultra-high vacuum standard. This allows the vacuum chamber 11 to be evacuated to an ultra-high vacuum state when the molecular pump and mechanical pump are operating in series, meaning the inside of the probe arm 32 is also under vacuum.

[0061] In one embodiment, the in-situ testing device further includes a coaxial shielded cable 50, which is connected between the vacuum power feeder 324 and the electrical characteristic detector 40. When one end of the probe 31 makes conductive contact with the Josephine junction on the quantum bit chip, the electrical characteristic signal of the Josephine junction (such as resistance, current, voltage, etc.) is obtained. The coaxial shielded cable 50 transmits the electrical characteristic signal to the electrical characteristic detector 40. Preferably, the electrical characteristic detector 40 includes a multimeter.

[0062] The diameter of the end of the probe 31 away from the probe arm 32 is 15-20 μm, preferably 20 μm.

[0063] like Figure 1 As shown, in one embodiment, the laser irradiation unit 20 includes a laser 21 and a lens 22. The laser 21 is used to generate laser light, and the lens 22 is disposed between the laser 21 and the viewing window 12 for collimating and focusing the laser light.

[0064] Another embodiment of the present invention also provides an in-situ testing method for a quantum bit chip, the method comprising:

[0065] Provide in-situ testing equipment;

[0066] Place the qubit chip to be tested on the sample stage 14 and contact one end of the probe 31 with the Josephine junction on the qubit chip to be tested.

[0067] The vacuum cavity 11 is vacuumized to an ultrahigh vacuum state;

[0068] The laser is generated by the laser irradiation unit 20 to irradiate the Josephson junction on the quantum bit chip;

[0069] The electrical characteristic signal of the Josephson junction on the quantum bit chip is acquired by the probe 31.

[0070] It can be understood that, based on the in-situ testing device provided by the application, the electrical characteristic signal of the Josephson junction on the quantum bit chip can be acquired before, after or during the irradiation treatment of the laser on the Josephson junction on the quantum bit chip.

[0071] As shown in Figure 3a , Figure 3b and Figure 3c , the Josephson junction in the embodiment is of a micron size order, as shown in Figure 3d , the Josephson junction in the embodiment includes an Al / AlOx / Al three-layer structure. Before, after or during the laser treatment of the quantum bit chip, the application can in-situ test the electrical characteristics of the Josephson junction on the quantum bit chip. It can be understood that the nonlinear electrical characteristics between the two superconducting thin films of the Josephson junction and the intermediate tunneling layer are directly related to the intrinsic properties of the material, so the in-situ testing of the application can better reflect the real and effective state of the chip compared with the traditional non-in-situ testing. In addition, the application effectively avoids the oxidation of water and oxygen to the quantum bit chip, and eliminates the influence of the ultrathin oxide layer on the electrical measurement of the quantum bit from the root.

[0072] The conventional method needs 10 min for single laser irradiation treatment, 30 min for sample transfer under the atmosphere of the probe table, 50 min for sample placement, pinning and micro-force feedback of the special probe table to break the ultrathin oxide layer, and 10 min for final resistance value testing. The in-situ testing device and testing method of the application do not need to transfer the quantum bit chip sample, avoid the exposure of the quantum bit chip to the atmosphere, and further avoid the oxidation of water and oxygen to the sample, thereby eliminating the step of breaking the ultrathin oxide layer. Therefore, the total testing time needs the time of single laser irradiation treatment and the time required for resistance testing. Therefore, the device of the application can improve the electrical testing efficiency of the quantum bit chip by several times compared with the conventional probe table.

[0073] From the above technical solutions, the application has the following beneficial effects:

[0074] The present application can realize laser irradiation operation and electrical test operation simultaneously by opening the vacuum cavity 11 in the test platform 10, and opening the window 12 and the probe interface 13 on the side wall of the test platform 10, realizes in-situ testing, does not need to transfer the quantum bit chip, avoids exposing it to the atmosphere, improves the accuracy and convenience of electrical characteristic measurement;

[0075] By setting the mechanical pump and the molecular pump in communication, and cooperating with the probe structure 30 communicated to the vacuum cavity through the butt welding flange, the vacuum cavity 11 is ensured to be in a closed state, and an ultrahigh vacuum environment is provided for the quantum bit chip, effectively avoiding the oxidation of water, oxygen and the like to the quantum bit chip, and eliminating the influence of the ultrathin oxide layer quantum bit electrical measurement from the root;

[0076] The present application does not need to construct a complex special probe system, saves material cost and reduces operation complexity.

[0077] For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0078] In addition, it should be understood that although the present application is described in the specification in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be properly combined to form other embodiments that those skilled in the art can understand.

Claims

1. An in-situ testing device for a quantum bit chip, characterized by, The in-situ testing device comprises a laser irradiation unit, a testing table, a probe structure and an electrical property detection device; The testing table is internally provided with a vacuum cavity, the side wall of the testing table is provided with a window and at least two probe interfaces in communication with the vacuum cavity, and the vacuum cavity is provided with a sample table for carrying a quantum bit chip; The laser irradiation unit is used for generating laser, and the laser enters the vacuum cavity from the window and irradiates the quantum bit chip; The probe structure comprises at least two groups of probe arms and probes, the probe arms pass through the probe interfaces, the first ends of the probe arms are located in the vacuum cavity, the second ends of the probe arms are located outside the vacuum cavity, the probes are fixedly installed at the first ends of the probe arms and electrically connected with the probe arms, the second ends of the probe arms are electrically connected with the electrical property detection device, the probe arms further comprise a connecting rod, a bellows, a first connecting piece and a vacuum electric feedthrough, the probes are fixedly installed at the first ends of the connecting rod and electrically connected with the connecting rod, the vacuum electric feedthrough is fixedly installed at the second ends of the connecting rod and electrically connected with the connecting rod, part of the connecting rod is located in the vacuum cavity, and part of the connecting rod is nested in the bellows, the first end of the bellows is fixedly connected with the first connecting piece, the second end of the bellows is sealingly connected with the vacuum electric feedthrough, and the vacuum electric feedthrough is electrically connected with the electrical property detection device.

2. The in-situ testing device for a quantum bit chip according to claim 1, wherein, The in-situ testing device further comprises a mechanical pump and a molecular pump, the molecular pump is in communication with the vacuum cavity, and the mechanical pump is in communication with the molecular pump.

3. The in-situ testing device for a quantum bit chip according to claim 2, characterized in that, The probe interface comprises a second connecting piece fixedly connected with the side wall of the testing table, and the first connecting piece and the second connecting piece are connected through a fixing piece.

4. The in-situ testing device for a quantum bit chip according to claim 3, characterized by, The first connecting piece comprises a first butt welding flange; and / or The second connecting piece comprises a second butt welding flange.

5. The in-situ testing device for a quantum bit chip of claim 2, wherein, The in-situ testing device further comprises a coaxial shielded cable connected between the vacuum electric feedthrough and the electrical property detection device.

6. The in-situ testing device for a quantum bit chip of claim 1, wherein, The electrical property detection device comprises a multimeter.

7. The in-situ testing device for a quantum bit chip of claim 1, wherein, The probe has a diameter of 15-20 μm at the end away from the probe arm.

8. The in-situ testing device for a quantum bit chip of claim 1, wherein, The laser irradiation unit comprises a laser and a lens, the lens is arranged between the laser and the window and is used for collimating and focusing the laser.

9. An in-situ testing method for a quantum bit chip, characterized by, The method comprises: providing the in-situ testing device according to any one of claims 1-8; placing a quantum bit chip to be tested on the sample table and contacting one end of the probe with a Josephson junction on the quantum bit chip to be tested; vacuumizing the vacuum cavity to an ultrahigh vacuum state; generating laser by the laser irradiation unit to irradiate the Josephson junction on the quantum bit chip; obtaining an electrical property signal of the Josephson junction on the quantum bit chip by the probe.

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