Diagnostic device

Abstract

The present application discloses a diagnostic device comprising: a probe; a motor configured to scan the probe over the test circuit; a superconducting quantum interference device (SQUID) attached to the probe and configured to be coupled to the test circuit such that electronic noise present in the test circuit causes a first current flowing through the SQUID; and a current path configured to receive a second current flowing through the SQUID. The SQUID is configured to generate an output in the form of a first voltage in response to a sum of the first current and the second current being less than a threshold current, and to generate an output in the form of a second voltage in response to a sum of the first current and the second current being greater than the threshold current.

Description

Technical Field

[0001] The present disclosure relates generally to a diagnostic device, and more particularly to a diagnostic device including a scanning probe configured to analyze electronic noise at different locations of a test circuit. Background Art

[0002] In some applications, complementary metal oxide semiconductor (CMOS) circuits operate at cryogenic temperatures (e.g., less than or equal to 4K (corresponding to liquid helium) or less than or equal to 77K (corresponding to liquid nitrogen)). Identifying the source of electronic noise can help troubleshoot such cryogenic circuits, however, current methods for analyzing noise from cryogenic circuits have some disadvantages. Conventional methods involve collecting signals in a cryogenic environment and examining them for electronic noise using equipment operating at room temperature. The process of transmitting signals from the cryogenic environment to room temperature introduces more thermal noise. As a result, noise from the cryogenic environment may be difficult to isolate from noise from the room temperature environment or transmission line noise along the thermal gradient between the cryogenic and room temperature environments. Therefore, there is a need for improved diagnostic equipment and improved diagnostic methods for analyzing electronic noise in a cryogenic environment. Summary of the invention

[0003] One aspect of the present disclosure is a diagnostic device comprising: a probe; a motor configured to scan the probe over a test circuit; a superconducting quantum interference device (SQUID) attached to the probe and configured to couple to the test circuit so that electronic noise present in the test circuit causes a first current to flow through the SQUID; and a current path configured to receive a second current flowing through the SQUID, wherein the SQUID is configured to: generate an output in the form of a first voltage in response to the sum of the first current and the second current being less than a threshold current, and to generate an output in the form of a second voltage in response to the sum of the first current and the second current being greater than the threshold current.

[0004] Another aspect of the present disclosure is a method of operating a diagnostic device, the method comprising: (a) moving a probe via a motor to a first position of a test circuit, wherein a superconducting quantum interference device (SQUID) is attached to the probe; (b) generating a first current within the SQUID in response to the SQUID detecting a first electronic noise at the first position of the test circuit; (c) increasing the amplitude of a second current flowing through the SQUID while generating the first current; (d) determining the amplitude of the second current at which the output of the SQUID changes from a first voltage to a second voltage when the probe is above the first position; (e) moving the probe via the motor to a second position of the test circuit; (f) generating a third current within the SQUID in response to the SQUID detecting a second electronic noise at the second position of the test circuit; (g) increasing the amplitude of the second current flowing through the SQUID while generating the third current; and (h) determining the amplitude of the second current at which the output of the SQUID changes from the first voltage to the second voltage when the probe is above the second position.

[0005] With reference to quantities or measurements described herein, the terms "about" or "substantially" mean that the characteristic, parameter or value described need not be achieved precisely, but deviations or changes (including, for example, tolerances, measurement errors, measurement accuracy limitations and other factors known to those skilled in the art) may occur in amounts that do not negate the effect that the characteristic is intended to provide.

[0006] The features, functions, and advantages that have been discussed can be achieved independently in various examples or may be combined in yet other examples, further details of which can be seen in the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The novel features believed characteristic of the illustrative examples are set forth in the appended claims. However, the illustrative examples together with the preferred mode of use, further objects and description thereof will be best understood by reference to the following detailed description of illustrative examples of the present disclosure when read in conjunction with the accompanying drawings.

[0008] Figure 1 is a schematic diagram of a diagnostic circuit and a test circuit according to one example.

[0009] Figure 2 A Gaussian distribution of the magnitude of the current causing the transition of the SQUID according to one example is shown.

[0010] Figure 3 Gaussian and white noise distributions of the amplitude of the current causing the transition of the SQUID according to one example are shown.

[0011] Figure 4 Gaussian distribution and shot noise distribution of the amplitude of the current causing the transition of the SQUID according to one example are shown.

[0012] Figure 5 Gaussian distribution and shot noise distribution of the amplitude of the current causing the transition of the SQUID according to one example are shown.

[0013] Figure 6 is a block diagram of a diagnostic device according to an example.

[0014] Figure 7 is a schematic diagram of a diagnostic device and test circuit according to one example, including an illustration of a SQUID.

[0015] Figure 8 is a block diagram of a diagnostic device according to an example.

[0016] Fig. 9 is a schematic diagram of a diagnostic system including a diagnostic device according to an example.

[0017] Fig.10 is a schematic diagram of a diagnostic system according to an example, the diagnostic system including a diagnostic device according to an example.

[0018] Fig.11 is a block diagram of a method according to an example.

[0019] Fig.12 is a block diagram of a method according to an example.

[0020] Fig.13 is a block diagram of a method according to an example.

[0021] Fig.14 is a block diagram of a method according to an example.

[0022] Fig.15 is a block diagram of a method according to an example.

[0023] Fig.16 is a block diagram of a method according to an example.

[0024] Fig.17 is a block diagram of a method according to an example.

[0025] Fig.18 is a block diagram of a method according to an example.

[0026] Fig.19 is a block diagram of a method according to an example.

[0027] Fig. 20is a block diagram of a method according to an example.

[0028] Fig.21 is a block diagram of a method according to an example.

[0029] Fig. 22 is a block diagram of a method according to an example.

[0030] Fig.23 is a block diagram of a method according to an example.

[0031] Fig.24 is a block diagram of a method according to an example. DETAILED DESCRIPTION

[0032] As noted above, there is a need for improved diagnostic devices and improved diagnostic methods for analyzing electronic noise in cryogenic environments, such as those included in the present disclosure.

[0033] A diagnostic device includes a probe (e.g., a scanning microscope probe) and a motor configured to scan the probe over a test circuit. The test circuit may be a CMOS circuit operating in a cryogenic environment. The diagnostic device also includes a SQUID, which is attached to the probe and configured to be coupled to the test circuit (e.g., inductively) so that electronic noise present in the test circuit causes a first current to flow through the SQUID. The SQUID typically includes two Josephson junctions connected together to form a loop around which a first current flows. The diagnostic device also includes a current path configured to receive a second current flowing through the SQUID. The SQUID is configured to generate an output in the form of a first voltage in response to the sum of the first current and the second current being less than a threshold current, and to generate an output in the form of a second voltage in response to the sum of the first current and the second current being greater than a threshold current.

[0034] A method of operating a diagnostic device includes moving a probe via a motor over a first position of a test circuit, and generating a first current within a SQUID in response to the SQUID detecting a first electronic noise at the first position of the test circuit. The method also includes increasing the amplitude of a second current flowing through the SQUID while generating the first current, and determining the amplitude of the second current at which the output of the SQUID transitions from a first voltage to a second voltage when the probe is over the first position. The method also includes moving the probe via a motor over a second position of the test circuit, and generating a third current within the SQUID in response to the SQUID detecting a second electronic noise at the second position of the test circuit. The method also includes increasing the amplitude of the second current flowing through the SQUID while generating the third current, and determining the amplitude of the second current at which the output of the SQUID transitions from a first voltage to a second voltage when the probe is over the second position.

[0035] Therefore, the output of the SQUID can indicate whether the sum of the first current caused by the electronic noise of the test circuit at the first position and the second current flowing through the current path is greater than or less than the threshold current of the SQUID. By controlling the amplitude of the second current flowing through the current path and noting the amplitude of the second current at which the output of the SQUID transitions when the probe is above the first position, the amplitude of the first current caused by the electronic noise at the first position of the test circuit can be inferred. By repeating this process multiple times, statistical techniques can be used to identify the characteristics of the electronic noise of the test circuit at the first position. Thermal noise introduced by the room temperature analysis environment does not obscure the information indicated by the binary output of the SQUID. By repeating this process at other positions of the test circuit, the electronic noise detected at different positions of the test circuit can also be compared.

[0036] The disclosed examples will now be described more fully below with reference to the accompanying drawings, in which some but not all of the disclosed examples are shown. In fact, several different examples may be described, and should not be construed as being limited to the examples set forth herein. Instead, these examples are described so that the disclosure will be comprehensive and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0037] Figure 1is a schematic diagram of a diagnostic circuit 10 and a test circuit 14. The diagnostic circuit 10 includes a SQUID 12 coupled (e.g., inductively) to the test circuit 14 such that electronic noise 15 present in the test circuit 14 causes a current 16A to flow through the SQUID 12. The diagnostic circuit 10 also includes a current path 18 configured to receive a current 16B flowing through the SQUID 12. The SQUID 12 is configured to generate an output V in the form of a first voltage in response to the sum of the current 16A and the current 16B being less than a threshold current. + 、V - , and generating an output V in the form of a second voltage in response to the sum of current 16A and current 16B being greater than a threshold current + 、V - The threshold current is usually on the order of microamperes.

[0038] The SQUID 12 includes a Josephson junction 11A and a Josephson junction 11B. The SQUID 12 forms a superconducting loop including two different superconducting materials that meet at the Josephson junction 11A and the Josephson junction 11B. The length, width, shape, and cross-sectional area of ​​the Josephson junction 11A and the Josephson junction 11B, the selection of the materials forming the Josephson junction 11A and the Josephson junction 11B, and the operating temperature of the SQUID 12 are equivalent to design variables or constraints that determine the threshold current corresponding to the SQUID 12.

[0039] The current path 18 is typically made of a superconducting material that is the same as one of the materials forming the Josephson junction 11A and the Josephson junction 11B.

[0040] As shown, the test lead 21 is arranged near one or more components of the test circuit 14 to capture the electronic noise 15 in the form of an induced current. The electronic noise 15 further causes a current 16A to flow within the loop of the SQUID 12. For clarity, only the current 16A circulating in the loop of the SQUID 12 is shown. However, part of the current 16B also passes through the loop between entering and leaving the loop. The current 16B is usually controlled and provided by an external current source.

[0041] As described above, if the sum of current 16A and current 16B is less than the threshold current, SQUID 12 will generate an output V in the form of a first voltage (eg, 0 V). + 、V - If the sum of current 16A and current 16B is greater than the threshold current, SQUID 12 will generate an output V in the form of a second voltage (eg, 5V). + 、V - SQUID 12 generates an output V between terminals 17A and 17B of SQUID 12.+ 、V - Typically, a first voltage corresponding to the sum of current 16A and current 16B being less than a threshold current is less than a second voltage corresponding to the sum of current 16A and current 16B being greater than a threshold current. In various examples, test circuit 14 (e.g., a CMOS circuit) operates in an environment cooled by liquid nitrogen and / or liquid helium.

[0042] In operation, diagnostic circuit 10 generates current 16A within SQUID 12 in response to SQUID 12 detecting electronic noise 15 within test circuit 14. While generating current 16A, diagnostic circuit 10 or an external current source increases the magnitude of current 16B flowing through SQUID 12. In addition, a computing device and / or a voltmeter determines the output V of SQUID 12. + 、V - The magnitude of current 16B at which the voltage changes from the first voltage to the second voltage.

[0043] In some examples, while diagnostic circuit 10 generates current 16A within SQUID 12, the magnitude of current 16B increases at a linear rate (or another controlled rate) with respect to time. The computing device and / or voltmeter determines the output V of SQUID 12. + 、V - The computing device then uses the magnitude of current 16B at the start of the ramp, the known ramp rate, and the time elapsed from the start of the ramp to the transition to infer the magnitude of current 16B when SQUID 12 transitions from the first voltage to the second voltage.

[0044] In some examples, current 16B is increased while current 16A is generated and the output V + 、V - The process of determining the magnitude of the current 16B at which the first voltage is changed to the second voltage is repeated multiple times. For example, the process can be repeated hundreds or thousands of times to obtain statistically significant data samples. That is, the obtained data can be used to determine the mean, median, variance or other metric that characterizes the electronic noise 15.

[0045] In some examples, current 16B is increased while current 16A is generated and the output V + 、V - The process of changing the amplitude of the current 16B at which the first voltage is changed to the second voltage is repeated multiple times using different gradient rates for the current 16B. For example, each process may use a continuously increasing gradient rate for the current 16B. Changing the gradient rate of the current 16B may help detect the electronic noise 15 of the test circuit 14 that occurs at different changing frequencies.

[0046] Figure 2 The Gaussian distribution of the amplitude of the current 16B that causes the transition of the SQUID 12 is shown. In this example, the electronic noise 15 mainly takes the form of thermal noise. In this example, an amplitude of about 100 μA is the most common amplitude of the current 16B that causes the transition of the SQUID 12. If at a given moment, the electronic noise 15 and the current 16A have high values, then a smaller amplitude of the current 16B will cause the output V + 、V - On the other hand, if the electronic noise 15 and the current 16A have low values, the larger magnitude of the current 16B will cause the output V + 、V - From a first voltage to a second voltage.

[0047] In some examples, it is useful to distinguish between the magnitude of current 16B that corresponds to a Gaussian distribution and the magnitude of current 16B that does not correspond to a Gaussian distribution. Figure 2 , all amplitudes of current 16B correspond to Gaussian distribution, which indicates that thermal activity is the main cause of electronic noise 15.

[0048] Figure 3 Another distribution of the amplitude of current 16B is shown which results in a transition of SQUID 12. In this example, there is a Gaussian component 61 and a non-Gaussian component 62. Gaussian component 61 represents the thermal noise of test circuit 14, while non-Gaussian component 62 represents the thermal noise of diagnostic circuit 10 in the form of white noise.

[0049] Figure 4 Another distribution of the amplitude of current 16B is shown which results in a transition of SQUID 12. In this example, there is a Gaussian component 61 and a non-Gaussian component 62. Gaussian component 61 represents the thermal noise of test circuit 14, while non-Gaussian component 62 represents the thermal noise of diagnostic circuit 10 in the form of a single source of shot noise.

[0050] Figure 5 Another distribution of the amplitude of current 16B is shown that results in a transition of SQUID 12. In this example, there is a Gaussian component 61 and a non-Gaussian component 62. Gaussian component 61 represents thermal noise of test circuit 14, while non-Gaussian component 62 represents thermal noise of diagnostic circuit 10 in the form of multiple sources of shot noise.

[0051] Figure 6 is a block diagram of the diagnostic device 20. The diagnostic device 20 includes a probe 22, a motor 24, a SQUID 12, and a current path 18.

[0052] Figure 7is a schematic diagram of diagnostic device 20 and test circuit 14 , including an illustration of SQUID 12 .

[0053] Motor 24 is configured to scan probe 22 over test circuit 14. Diagnostic device 20 also includes SQUID 12 attached to probe 22 and configured to couple to test circuit 14 (eg, inductively) as motor 24 moves probe 22 to different locations over test circuit 14.

[0054] Depending on the position of the probe 22 over the test circuit 14, the electronic noise 15A or the electronic noise 15B present in the test circuit 14 causes a current 16A to flow through the SQUID 12. The diagnostic device 20 also includes a current path 18 configured to receive the current 16B flowing through the SQUID 12. The SQUID 12 is configured to generate an output V in the form of a first voltage in response to the sum of the current 16A and the current 16B being less than a threshold current. + 、V - , and generating an output V in the form of a second voltage in response to the sum of current 16A and current 16B being greater than a threshold current + 、V - .

[0055] The probe 22 generally takes the form of any probe used for a scanning probe microscope. The motor 24 generally takes the form of any motor that can control the three-dimensional positioning of the probe 22 relative to the test circuit 14. The motor 24 can be used to scan the probe 22 over the test circuit 14 to analyze the electronic noise 15 at different locations of the test circuit 14. That is, the motor 24 is configured to move the probe 22 along an x-axis and a y-axis that are orthogonal to each other and parallel to the test circuit 14. The motor 24 is also configured to move the probe 22 along a z-axis that is orthogonal to the x-axis, the y-axis, and the test circuit 14.

[0056] As shown, SQUID 12 is scanned by motor 24 with probe 22 to capture electronic noise 15 in the form of induced current. Electronic noise 15 further induces current 16A flowing within the loop of SQUID 12. Current 16B is typically controlled and provided by an external current source operatively coupled to diagnostic device 20.

[0057] In operation, motor 24 moves probe 22 over position 19A of test circuit 14, causing SQUID 12 to generate current 16A within SQUID 12 in response to SQUID 12 detecting electronic noise 15A at position 19A of test circuit 14. While current 16A is being generated, current 16B is increased via an external current source. When probe 22 is over position 19A, computing device determines that the output V of SQUID 12 is 16A. +、V - The magnitude of current 16B at which the voltage changes from the first voltage to the second voltage.

[0058] Next, motor 24 moves probe 22 over position 19B of test circuit 14, causing SQUID 12 to generate current 16A in response to SQUID 12 detecting electronic noise 15B at position 19B of test circuit 14. While current 16A is being generated, current 16B is increased via an external current source. When probe 22 is over position 19B, the computing device determines that the output V of SQUID 12 is + 、V - The magnitude of current 16B at which the voltage changes from the first voltage to the second voltage.

[0059] As mentioned above Figure 2-Figure 5 As described above, while generating current 16A, current 16B is increased and the output V is determined. + 、V - The process of determining the magnitude of the current 16B at which the first voltage is changed to the second voltage can be repeated multiple times for the location 19A and multiple times for the location 19B. For example, the process can be repeated hundreds or thousands of times for each location to obtain a statistically significant data sample for each location. That is, the obtained data can be used to determine the mean, median, variance or other metric that characterizes the electronic noise 15 at each location. As described above with reference to Figure 2-Figure 5 As described, the magnitude of the current 16B causing the transition at each location can be classified as corresponding to or not corresponding to a Gaussian distribution. Likewise, the above-described process using different gradient rates of the current 16B can also be used at each location.

[0060] Figure 8 is a block diagram of a diagnostic device 30. The diagnostic device 30 includes an array 32A of SQUIDs 12. The diagnostic device 30 also includes a current source 34. The current source 34 may include any circuit that can be controlled to generate a desired current amplitude and provide the current to another circuit.

[0061] Fig. 9is a schematic diagram of a diagnostic system 40 including a diagnostic device 30. The diagnostic system 40 includes an array 32B of test circuits 14A-14F and an array 32A of SQUIDs 12A-12F. When the array 32A is appropriately positioned above the array 32B, each SQUID 12A-12F of the array 32A is respectively (e.g., inductively) coupled to the test circuits 14A-14F of the array 32B, such that electronic noise present in the test circuits 14A-14F causes a current 16A to flow through the corresponding SQUID 12A-12F. The diagnostic system 40 also includes a current source 34 (e.g., a multi-output current source) configured to provide a current 16B to each SQUID 12A-12F of the array 32A, such that the current 16B flows through the SQUIDs 12A-12F, respectively. Each SQUID 12A-12F of array 32A is configured to generate its own output V in the form of a first voltage (eg, 0 V) ​​in response to the sum of current 16A and current 16B being less than a threshold current. + 、V - , and generates its own output V in the form of a second voltage (e.g., 5V) in response to the sum of current 16A and current 16B being greater than a threshold current + 、V - .

[0062] In operation, in response to detecting electronic noise 15 within test circuits 14A-14F, respectively, diagnostic device 30 generates current 16A within SQUIDs 12A-12F for each SQUID 12A-12F of array 32A and corresponding test circuits 14A-14F of array 32B. While generating current 16A within SQUIDs 12A-12F, diagnostic device 30 (e.g., current source 34) increases the magnitude of current 16B flowing through the corresponding SQUIDs 12A-12F. In addition, the computing device and / or voltmeter determines, for each SQUID 12A-12F of array 32A, the output V of SQUID 12A-12F. + 、V - The magnitude of current 16B at which the voltage changes from the first voltage to the second voltage.

[0063] refer to Fig.10, the diagnostic device 30 is used to analyze the new array of test circuits 14. Therefore, the diagnostic device 30 is moved to the array 32C in close proximity to the test circuits 14G-14L. Therefore, in response to detecting the electronic noise 15 in the test circuits 14G-14L, respectively, the diagnostic device 30 generates a current 16A in the SQUIDs 12A-12F for each SQUID 12A-12F of the array 32A and the corresponding test circuits 14G-14L of the array 32C. While generating the current 16A in the SQUIDs 12A-12F, the diagnostic device 30 (e.g., the current source 34) increases the amplitude of the current 16B flowing through the corresponding SQUIDs 12A-12F. In addition, the computing device and / or the voltmeter determines, for each SQUID 12A-12F of the array 32A, the output V of the SQUID 12A-12F. + 、V - The magnitude of current 16B at which the voltage changes from the first voltage to the second voltage.

[0064] As mentioned above Figure 2-Figure 5 As described above, while generating current 16A, current 16B is increased and the output V is determined. + 、V - The process of determining the magnitude of the current 16B at which the first voltage is changed to the second voltage may be repeated multiple times for each test circuit 14A-14F of the array 32B, and repeated multiple times for each test circuit 14G-14L of the array 32C. For example, the process may be repeated hundreds or thousands of times for each test device of each array to obtain a statistically significant data sample for each test device of each array. That is, the obtained data may be used to determine a mean, median, variance, or other metric that characterizes the electronic noise 15 at each test device of each array.

[0065] As mentioned above Figure 2-Figure 5 As described, the respective amplitudes of the current 16B that cause the transitions of each SQUID of each array can be classified as corresponding to or not corresponding to a Gaussian distribution. Likewise, the above process of using different ramp rates of the current 16B can also be used for each SQUID of each array.

[0066] Figure 11-Figure 14 is a block diagram of methods 100 , 110 , 114 , and 118 of operating the diagnostic circuit 10 . Figure 15-19 is a block diagram of method 200 , method 218 , method 224 , and method 228 of operating diagnostic device 20 . Figure 20-24 is a block diagram of methods 300, 310, 322, 324, and 326 for operating diagnostic device 30. Figure 11-Figure 24As shown, methods 200-326 include one or more operations, functions, or actions, as shown in blocks 102, 104, 106, 108, 112, 116, 202, 204, 206, 208, 210, 212, 214, 216, 220, 222, 226, 302, 304, 306, 308, 312, 314, 316, 318, 320, and 328. Although these blocks are shown in sequence, these blocks may also be performed in parallel and / or in a different order than those described herein. In addition, various blocks may be combined into fewer blocks, divided into additional blocks, and / or removed based on the desired implementation.

[0067] At block 102, method 100 includes (a) generating a current 16A within SQUID 12 in response to SQUID 12 detecting electronic noise 15 within test circuit 14. Figure 1 Functionality associated with block 102 is discussed.

[0068] At block 104, method 100 includes (b) increasing the magnitude of current 16B flowing through SQUID 12 while generating current 16A. Figure 1 Functionality associated with block 104 is discussed.

[0069] At block 106, method 100 includes (c) determining an output V of SQUID 12. + 、V - The magnitude of the current 16B at which the first voltage changes to the second voltage. Figure 1-Figure 5 Functionality associated with block 106 is discussed.

[0070] At block 108, method 110 includes identifying a magnitude of current 16B corresponding to a Gaussian distribution. Figure 2-Figure 5 Functionality associated with block 108 is discussed.

[0071] At block 112, method 114 includes identifying a magnitude of current 16B that does not correspond to a Gaussian distribution. Figure 3-Figure 5 Functionality associated with block 112 is discussed.

[0072] At block 116, method 118 includes performing steps (a), (b), and (c) a second time, wherein the second time performing step (b) includes increasing the magnitude of current 16B at a second rate greater than the first rate. Figure 1 Functionality associated with block 116 is discussed.

[0073] At block 202, method 200 includes (a) moving probe 22 via motor 24 to a position 19A of test circuit 14, wherein SQUID 12 is attached to probe 22. Figure 7 The functionality associated with block 202 is discussed.

[0074] At block 204, method 200 includes (b) generating current 16A within SQUID 12 in response to SQUID 12 detecting electronic noise 15A at location 19A of test circuit 14. Figure 7 Functionality associated with block 204 is discussed.

[0075] At block 206, method 200 includes (c) increasing the magnitude of current 16B flowing through SQUID 12 while generating current 16A. Figure 7 Functionality associated with block 206 is discussed.

[0076] At block 208, method 200 includes (d) determining the output V of SQUID 12 when probe 22 is above position 19A. + 、V - The magnitude of the current 16B at which the first voltage changes to the second voltage. Figure 7 Functionality associated with block 208 is discussed.

[0077] At block 210, method 200 includes (e) moving probe 22 via motor 24 to position 19B of test circuit 14. Figure 7 Functionality associated with block 210 is discussed.

[0078] At block 212, method 200 includes (f) generating current 16A within SQUID 12 in response to SQUID 12 detecting electronic noise 15B at location 19B of test circuit 14. Figure 7 The functionality associated with block 212 is discussed.

[0079] At block 214, method 200 includes (g) increasing the magnitude of current 16B flowing through SQUID 12 while generating current 16A. Figure 7 Functionality associated with block 214 is discussed.

[0080] At block 216, method 200 includes (h) determining the output V of SQUID 12 when probe 22 is above position 19B. + 、V - The magnitude of the current 16B at which the first voltage changes to the second voltage. Figure 7 Functionality associated with block 216 is discussed.

[0081] At block 220, method 218 includes identifying a magnitude of current 16B corresponding to a Gaussian distribution. Figure 2-Figure 5 The functionality associated with block 220 is discussed.

[0082] At block 222, method 224 includes identifying a magnitude of current 16B that does not correspond to a Gaussian distribution. Figure 3-Figure 5 Functionality associated with block 222 is discussed.

[0083] At block 226, method 228 includes performing steps (b), (c), and (d) a second time, wherein the second time performing step (c) includes increasing the magnitude of current 16B at a second rate greater than the first rate. Figure 7 Functionality associated with block 222 is discussed.

[0084] At block 302, method 300 includes (a) generating a current 16A within SQUID 12 for each SQUID 12A-12F of array 32A of SQUIDs 12A-12F and a corresponding test circuit 14A-14F of array 32B of test circuits 14A-14F in response to detecting electronic noise 15 within test circuit 14. Fig. 9 Functionality associated with block 302 is discussed.

[0085] At block 304, method 300 includes (b) for each SQUID 12A-12F of array 32A, increasing the magnitude of current 16B flowing through SQUID 12A-12F while generating current 16A. Fig. 9 Functionality associated with block 304 is discussed.

[0086] At block 306, method 300 includes (c) determining, for each SQUID 12A-12F in array 32A, an output V + 、V - The magnitude of the current 16B at which the first voltage is changed to the second voltage. Fig. 9 Functionality associated with block 306 is discussed.

[0087] At block 308, method 310 includes moving diagnostic device 30 after performing steps (a), (b), and (c). Fig. 9 and Fig.10 Functionality associated with block 308 is discussed.

[0088] At block 312, method 310 includes generating a current 16A within SQUID 12A-12F for each SQUID 12A-12F of array 32A and corresponding test circuit 14G-14J of array 32C of test circuits 14G-14J in response to detecting electronic noise 15 within test circuit 14G-14J. Fig.10 Functionality associated with block 312 is discussed.

[0089] At block 314, the method 310 includes, for each SQUID 12A-12F of the array 32A, increasing the magnitude of the current 16B flowing through the SQUID 12A-12F while generating the current 16A. Fig.10 Functionality associated with block 314 is discussed.

[0090] At block 316, method 310 includes determining, for each SQUID 12A-12F in array 32A, the output V + 、V - The magnitude of the current 16B at which the first voltage changes to the second voltage. Fig.10 Functionality associated with block 316 is discussed.

[0091] At block 318, method 322 includes identifying, for each test circuit 14A-14F of array 32B, a magnitude of current 16B corresponding to a Gaussian distribution. Figure 2-Figure 5 Functionality associated with block 318 is discussed.

[0092] At block 320, method 324 includes identifying, for each test circuit 14A-14F of array 32B, a magnitude of current 16B that does not correspond to a Gaussian distribution. Figure 3-Figure 5 Functionality associated with block 320 is discussed.

[0093] At block 328, method 326 includes performing steps (a), (b), and (c) a second time, wherein the second time performing step (b) includes increasing the magnitude of current 16B at a second rate greater than the first rate. Fig. 9 Functionality associated with block 328 is discussed.

[0094] The descriptions of different advantageous arrangements are presented for purposes of illustration and description and are not intended to be exhaustive or limited to the examples of the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. In addition, different advantageous examples may describe different advantages compared to other advantageous examples. The selected one or more examples are selected and described in order to explain the principles of the examples, the practical application, and to enable others of ordinary skill in the art to understand the disclosure of various examples with various modifications suitable for the specific purposes contemplated.

Claims

1. A diagnostic device (20) comprising: include: Probe (22); a motor (24) configured to scan the probe over the test circuit (14); a superconducting quantum interference device (SQUID) (12) attached to the probe and configured to couple to the test circuit such that electronic noise (15) present in the test circuit causes a first current (16A) to flow through the SQUID; and a current path (18) configured to receive a second current (16B) flowing through the SQUID, wherein the SQUID is configured to: In response to the sum of the first current and the second current being less than a threshold current, an output in the form of a first voltage (V + 、V - ),as well as In response to the sum of the first current and the second current being greater than the threshold current, an output in the form of a second voltage (V + 、V - ). 2 . The diagnostic device of claim 1 , wherein the SQUID is configured to be inductively coupled to the test circuit.

3. The diagnostic device of claim 1, wherein the motor is configured to move the probe along a first axis (x) and a second axis (y) that are orthogonal to each other and parallel to the test circuit.

4. The diagnostic device of claim 3, wherein the motor is configured to move the probe along a third axis (z) orthogonal to the first axis, the second axis, and the test circuit.

5. The diagnostic apparatus of claim 1, wherein the first voltage is substantially equal to zero. The diagnostic apparatus of claim 1 , wherein the first voltage is less than the second voltage. The diagnostic apparatus of claim 1 , wherein the second voltage is greater than zero.

8. A method (200) of operating a diagnostic device (20), the method include: (202)(a) moving a probe (22) via a motor (24) to a first position (19A) above a test circuit (14), wherein a superconducting quantum interference device (SQUID) (12) is attached to the probe; (204)(b) generating a first current (16A) within the SQUID in response to the SQUID detecting a first electronic noise (15A) at the first location of the test circuit; (206)(c) increasing the amplitude of a second current (16B) flowing through the SQUID while generating the first current; (208)(d) determining the output (V) of the SQUID when the probe is at the first position. + 、V - ) the amplitude of the second current at which the voltage changes from the first voltage to the second voltage; (210)(e) moving the probe via the motor to a second position (19B) above the test circuit; (212)(f) generating a third current (16A) within the SQUID in response to the SQUID detecting a second electronic noise (15B) at the second location of the test circuit; (214)(g) increasing the amplitude of the second current flowing through the SQUID while generating the third current; and (216)(h) When the probe is at the second position, determining the amplitude of the second current at which the output of the SQUID transitions from the first voltage to the second voltage.

9. The method of claim 8, wherein the method comprises performing steps (b), (c) and (d) at least twice before performing steps (e), (f), (g) and (h).

10. The method of claim 9, further comprising (220) identifying the magnitude of the second current corresponding to a Gaussian distribution.

11. The method of claim 10, further comprising (222) identifying the magnitude of the second current that does not correspond to the Gaussian distribution.

12. The method of claim 8, wherein increasing the amplitude of the second current while generating the first current comprises increasing the amplitude at a first rate, the method further comprising (226) performing steps (b), (c), and (d) a second time, wherein performing step (c) a second time comprises increasing the amplitude at a second rate greater than the first rate.

13. The method of claim 8, wherein the method is performed while the test circuit is operating in an environment cooled by liquid nitrogen.

14. The method of claim 8, wherein the method is performed while the test circuit is operating in an environment cooled by liquid helium.

15. The method of claim 8, wherein generating the first current comprises generating the first current via inductive coupling between the SQUID and the test circuit. The method of claim 8 , wherein the first voltage is substantially equal to zero. The method of claim 8 , wherein the first voltage is less than the second voltage. The method of claim 8 , wherein the second voltage is greater than zero.

19. The method of claim 8, wherein the test circuit comprises a complementary metal oxide semiconductor (CMOS) circuit.

20. The method of claim 8, wherein moving the probe to the second position over the test circuit comprises moving the probe along a first axis (x) and a second axis (y) that are orthogonal to each other and parallel to the test circuit.

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