US20160254434A1 - Systems and Methods for Suppressing Magnetically Active Surface Defects in Superconducting Circuits - Google Patents
Systems and Methods for Suppressing Magnetically Active Surface Defects in Superconducting Circuits Download PDFInfo
- Publication number
- US20160254434A1 US20160254434A1 US14/632,505 US201514632505A US2016254434A1 US 20160254434 A1 US20160254434 A1 US 20160254434A1 US 201514632505 A US201514632505 A US 201514632505A US 2016254434 A1 US2016254434 A1 US 2016254434A1
- Authority
- US
- United States
- Prior art keywords
- circuits
- hermetic enclosure
- superconducting
- superconducting quantum
- qubit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 77
- 230000007547 defect Effects 0.000 title claims abstract description 38
- 238000005538 encapsulation Methods 0.000 claims abstract description 13
- 239000011261 inert gas Substances 0.000 claims abstract description 11
- 239000011248 coating agent Substances 0.000 claims abstract description 6
- 238000000576 coating method Methods 0.000 claims abstract description 6
- 230000001678 irradiating effect Effects 0.000 claims abstract description 5
- 239000002096 quantum dot Substances 0.000 claims description 37
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 16
- 239000001301 oxygen Substances 0.000 claims description 16
- 229910052760 oxygen Inorganic materials 0.000 claims description 16
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 11
- 230000003028 elevating effect Effects 0.000 claims description 4
- 230000008569 process Effects 0.000 description 23
- 230000004907 flux Effects 0.000 description 17
- 239000000463 material Substances 0.000 description 11
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 10
- 238000001179 sorption measurement Methods 0.000 description 10
- 229910052782 aluminium Inorganic materials 0.000 description 9
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 9
- 229910001882 dioxygen Inorganic materials 0.000 description 9
- 239000010409 thin film Substances 0.000 description 8
- 241000238366 Cephalopoda Species 0.000 description 7
- 239000002156 adsorbate Substances 0.000 description 6
- 238000000384 X-ray magnetic circular dichroism spectroscopy Methods 0.000 description 5
- 238000000862 absorption spectrum Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000013459 approach Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 229910052758 niobium Inorganic materials 0.000 description 3
- 239000010955 niobium Substances 0.000 description 3
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910000883 Ti6Al4V Inorganic materials 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 238000002983 circular dichroism Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000010365 information processing Effects 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000000116 mitigating effect Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000001993 wax Substances 0.000 description 2
- 238000003775 Density Functional Theory Methods 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000000205 computational method Methods 0.000 description 1
- 235000009508 confectionery Nutrition 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 125000003700 epoxy group Chemical group 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000010943 off-gassing Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Images
Classifications
-
- H01L39/045—
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06N—COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
- G06N10/00—Quantum computing, i.e. information processing based on quantum-mechanical phenomena
-
- H01L27/18—
-
- H01L39/2493—
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N60/00—Superconducting devices
- H10N60/01—Manufacture or treatment
- H10N60/0912—Manufacture or treatment of Josephson-effect devices
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N60/00—Superconducting devices
- H10N60/80—Constructional details
- H10N60/81—Containers; Mountings
- H10N60/815—Containers; Mountings for Josephson-effect devices
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N69/00—Integrated devices, or assemblies of multiple devices, comprising at least one superconducting element covered by group H10N60/00
Definitions
- the field of the disclosure is directed to superconducting quantum circuits and devices. More particularly, the disclosure is directed to systems and methods related to quantum information processing and quantum computation.
- Superconducting integrated circuits are finding increased use in a variety of applications. For instance, in the field of quantum computation, the performance of superconducting quantum bits (“qubits”) has advanced rapidly in recent years, with preliminary multi-qubit implementations leading toward scalable, surface code architectures.
- quantum computation In contrast to classical computational methods that rely on binary data stored in the form of definite on/off states, or bits, methods in quantum computation take advantage of the quantum mechanical nature of superconducting quantum systems, which may be represented using a superposition of multiple quantum states.
- the present disclosure introduces a novel approach for controlling noise in superconducting quantum circuits that overcomes the drawbacks of previous technologies.
- the present disclosure recognizes that dominant sources of noise can arrive via molecular species found in ambient surroundings, rather than inherently from materials and geometries utilized therein.
- molecular oxygen is a magnetically active species that exhibits long range magnetic order at low temperatures and pressures. Adsorption of molecular oxygen can lead to appreciable magnetic noise in superconducting quantum circuits, such as superconducting qubits. Therefore, in accordance with the present invention, provided systems and methods are directed to controlling the proximate environment of superconducting quantum circuits. By suppressing surface effects, such as magnetically active defects, sources of noise can be appreciably reduced or eliminated.
- a method for reducing magnetic noise in qubit circuits includes providing one or more qubit circuits, and arranging the one or more qubit circuits in a hermetic enclosure capable of isolating the one or more qubit circuits from ambient surroundings.
- the method also includes controlling a background pressure of one or more magnetically active species in the hermetic enclosure to suppress magnetically active surface defects associated with the one or more qubit circuits.
- a system for suppressing magnetically active surface defects in superconducting quantum circuits includes a hermetic enclosure configured to accommodate therein one or more superconducting quantum circuits, and capable of isolating the one or more superconducting circuits from ambient surroundings.
- the system also includes a vacuum system removably coupled to the hermetic enclosure, and configured to control an environment in the hermetic enclosure such that magnetically active surface defects associated with the one or more superconducting quantum circuits are suppressed.
- a method for suppressing magnetically active surface defects in superconducting quantum circuits includes providing one or more superconducting quantum circuits, and arranging the one or more superconducting quantum circuits in a hermetic enclosure. The method also includes controlling an environment in the hermetic enclosure to suppress magnetically active surface defects associated with the one or more superconducting quantum circuits.
- FIG. 1 shows a flowchart setting forth steps of a method in accordance with the present disclosure.
- FIG. 2 shows another flowchart setting forth steps of a method in accordance with the present disclosure.
- FIG. 3A shows an example hermetic enclosure in accordance with aspects of the present disclosure.
- FIG. 3B shows an example of vacuum enclosure for use in coating the surfaces of superconducting circuits with non-magnetic encapsulation layers to prevent subsequent adsorption of magnetically active defects, in accordance with aspects of the present disclosure.
- FIG. 4 is a graph showing oxygen x-ray magnetic circular dichroism (“XMCD”) signal for thin film air-dosed aluminum as a function of magnetic field at 10 Kelvin.
- XMCD oxygen x-ray magnetic circular dichroism
- FIG. 5 is a graph of X-ray absorption spectra for thin film air-dosed aluminum indicating the presence of adsorbed molecular oxygen for temperatures below 50 Kelvin.
- FIG. 6 is another graph of X-ray absorption spectra for thin film air-dosed aluminum indicating the presence of adsorbed molecular oxygen for temperatures below 50 Kelvin.
- FIG. 7 is a graph illustrating the effect of ammonia exposure on a superconducting quantum interference device (“SQUID”).
- SQUID superconducting quantum interference device
- FIG. 8 is a graph illustrating the effect of ultraviolet light exposure on a SQUID.
- FIG. 9 is a graph illustrating the effect of ultraviolet light power on a SQUID.
- the present disclosure describes systems and methods directed to controlling the environment of superconducting quantum circuits for purposes including mitigating potential sources of noise, such as magnetic noise, found therein.
- the density of surface defects such as magnetically active surface defects, may reduced by limiting or prevention exposure to, and/or inducing desorption of active adsorbates, such as oxygen-containing adsorbates.
- the process 100 may begin at process block 102 where one or more superconducting quantum circuit(s), such as qubit circuits, may be provided.
- the one or more superconducting quantum circuit(s) may be fabricated at process block 102 in accordance with standard device practice.
- the surface of the superconducting quantum circuit(s) may be coated with a non-magnetic encapsulation layer. This may be advantageous particularly to devices that are sensitive to magnetically active defects and magnetic noise.
- candidate materials can include waxes, similar to the etch resist Apiezon W, with layer thicknesses on the order of millimeters, although other materials and layer thickness may be possible.
- the superconducting quantum circuit(s) may then be arranged or positioned in a hermetic enclosure configured to accommodate therein one or more superconducting quantum circuits.
- the sealable hermetic enclosure can be configured in any manner, and capable of a range of functionality, including isolating the superconducting quantum circuit(s) from ambient surroundings.
- this step can include generating a vacuum or near-vacuum environment, for instance, by operating a vacuum system coupled to the hermetic enclosure.
- the vacuum system may be capable of controlling the background pressure of the hermetic enclosure such that high vacuum or ultrahigh vacuum conditions are achieved.
- a high vacuum can be in a pressure range roughly between 10 ⁇ 6 to 10 ⁇ 8 Torr
- ultrahigh vacuum can be in a range of 10 ⁇ 8 Torr or lower, although other pressure values may be possible.
- the temperature of the hermetic enclosure may be elevated while reducing the pressure therein in order to bake out, or desorb, and subsequently remove active adsorbates or contaminants present in or about the enclosure walls.
- the native surface of the superconducting circuits can be passivated or modified at process block 106 , for example, by backfilling, or pressurizing, the hermetic enclosure after evacuation with an inert or nonmagnetic gas, such as ammonia gas.
- the surface of the superconducting circuits can also be irradiated using light at process block 106 , for instance, while performing a device cool-down protocol in order to promote photodesorption of active adsorbates.
- ultraviolet light may be used to irradiate the superconducting circuit(s).
- the density of one or more active species may be controlled such that sources of noise can be appreciably reduced.
- any such steps can be applied to the superconducting quantum circuit(s) or portions thereof that are sensitive to noise and dephasing, and are particularly relevant to large-scale multi-qubit circuits for gate-based quantum computing or quantum annealing.
- FIG. 2 another flowchart setting forth steps of a process 200 in accordance with aspects of the present disclosure is shown.
- the process 200 may begin at process block 202 where one or more qubit circuit(s) or devices are arranged or positioned in a hermetic enclosure.
- the environment in the hermetic enclosure may be controlled by reducing background pressure to obtain a target coverage, or lack thereof, of magnetic, as well as other undesirable adsorbates, on the surface of the qubit circuit(s). As described, this can be achieved by evacuating the hermetic enclosure to a high or ultrahigh vacuum, while optionally baking out the enclosure. In some aspects, as indicated by process block 206 , evacuation may also be followed by backfilling the enclosure with inert gases in order to occupy available adsorption sites at the surface of the qubit circuit(s), thus preventing the adsorption of residual magnetically active species, such as molecular oxygen.
- ammonia gas may be a suitable candidate for passivating a device surface such that magnetically active surface defects are suppressed, although other gases are also possible.
- the qubit circuit(s) may then be operated with a suppressed density of surface defects.
- qubit circuit(s) may particularly benefit from a reduced density of magnetically active surface defects that would reduce sources of noise, decoherence and dephasing.
- further control in the density of magnetically active adsorbed defects can include irradiation of the qubit circuit(s) in the hermetic enclosure with light, such as ultraviolet light, either during the evacuation process at process block 204 , and/or during a cool down process associated with operation at process block 208 .
- a system for suppressing magnetically active surface defects in superconducting quantum circuits can include a hermetic enclosure configured to accommodate therein at least one or more superconducting quantum circuits, such as qubit circuits, and a vacuum system removably coupled to the hermetic enclosure, and configured to control an environment in the hermetic enclosure such that surface defects, such as magnetically active surface defects, associated with the superconducting quantum circuits are suppressed.
- the hermetic enclosure can be designed in any manner, and include capabilities for controlling and operating devices, circuits or circuit components, including superconducting quantum circuits, arranged therein.
- the hermetic enclosure may be capable of isolating such devices, circuits or circuit components from ambient surroundings. This may be implemented using various features or elements suitable for achieving and sustaining vacuum or near-vacuum conditions, pressurized conditions, low-temperature conditions, and so forth.
- the hermetic enclosure may contain all-metal seals, such as conflat gaskets, and be constructed from welded aluminum with aluminum-stainless steel bimetal flanges for the vacuum seals, or may be constructed from an alloy of titanium machined to form knife edges for use in producing vacuum seals.
- the hermetic enclosure may be constructed in other ways as well.
- the hermetic enclosure may include, for instance, configurations for mitigating, reducing or eliminating sources of noise found in ambient surroundings, such as thermal, electrical, and magnetic sources of noise, and other sources of noise.
- the hermetic enclosure may configured to include or accommodate a heat source for elevating a temperature of the hermetic enclosure, for example, during an evacuation process.
- the hermetic enclosure may also include a light source, such as an LED device, capable of irradiating devices, circuits or circuit components therein using light, such as ultraviolet light.
- the light source may be operated during a cooling procedure, such that active species present on the surface of the superconducting circuits are desorbed.
- FIG. 3A shows an example hermetic enclosure 300 in accordance with aspects of the present disclosure.
- the hermetic enclosure 300 may be constructed using a first enclosing portion 302 and second enclosing portion 304 , which when coupled together via a metallic seal, or other seal, can provide vacuum-tight enclosure.
- the hermetic enclosure 300 is shown to include a number of electrical feedthroughs 306 connectable to circuits arranged therein, although it may be appreciated that other types of feedthroughs are possible.
- the hermetic enclosure also includes a sealable evacuation port 308 configured to be coupled to the vacuum system such that environment in the hermetic enclosure 300 can be controlled.
- the hermetic enclosure 300 may be manufactured using any materials suitable for controlling an environment therein.
- the hermetic enclosure may be fabricated from grade 5 titanium alloy (Ti—6Al—4V), with the following advantageous properties: 1) the material is hard enough to form an ultrahigh vacuum conflat seal; 2) the material is known for its low outgassing and is compatible with the desired ultrahigh vacuum environment; 3) there are commercially available weld-in hermetic wiring feedthroughs, for example of the SMA type, enabling high-bandwidth electrical connections into an ultrahigh vacuum environment; 4) Grade 5 titanium is a nonmagnetic material that is superconducting at low temperatures. This provides magnetic shielding for circuits or devices assembled in the hermetic enclosure 300 that are sensitive to external magnetic field fluctuations.
- the vacuum system (not shown in FIG. 3A ) may be configured to control a background pressure of one or more active species in the hermetic enclosure 300 , such as magnetically active species like molecular oxygen. As described, this may be achieved by evacuating the hermetic enclosure 300 to a high or ultrahigh vacuum, and optionally baking out the hermetic enclosure 300 using a heat source.
- the vacuum system may be configured to introduce inert gases into the hermetic enclosure 300 in order to passivate active surface defects of the superconducting circuits therein, the inert gas occupying available adsorption sites.
- inert gases such as ammonia gas may be utilized, although other gases may also be possible. In the case of qubit circuits, this would prevent surface adsorption of residual magnetically active species, such as molecular oxygen, and hence further suppress sources of qubit decoherence and dephasing.
- FIG. 3B an example of vacuum enclosure 350 , for use in coating the surfaces of superconducting circuits with non-magnetic encapsulation layers, is shown.
- Such encapsulation layers would prevent adsorption of magnetically active defects found in close proximity to the superconducting circuits, where coupling to the surface defects is strong.
- non-magnetic encapsulation materials for use in the vacuum enclosure 350 may include etch resist waxes, such as Apiezon W, or UHV-compatible epoxies, such as Torr Seal or Epo-tek, but other encapsulation materials are possible.
- the vacuum enclosure 350 may include a broad range of functionality, including capabilities for controlling an environment therein, for instance, by reducing ambient pressure to achieve vacuum or near vacuum conditions, or a targeted background pressure.
- the vacuum enclosure 350 may be configured with capabilities to dispense or deposit non-magnetic encapsulation layers upon surfaces of superconducting circuits therein.
- the vacuum enclosure 350 can include an inlet 352 configured to dispense non-magnetic encapsulation layers using a dispensing tube 354 .
- a dispensing tube 354 it may be appreciated, however, that other methods for coating the surface of a device inside the vacuum enclosure 350 , using a non-magnetic encapsulation layer, may be possible.
- the device can be exposed to atmosphere, as well as cooled to low temperatures in a non-hermetic enclosure, without appreciably deleterious consequences, since any magnetically active defects would be prevented from adsorbing in close proximity to the device.
- FIG. 4 shows a graph of oxygen XMCD signal for thin film air-dosed aluminum as a function of magnetic field at 10 Kelvin. Differences in x-ray absorption for the opposite x-ray helicities reveal the orbital, and in some cases spin, polarization of the hole states to which the photoelectrons are promoted.
- Oxygen and aluminum K-edges of native aluminum films, and the oxygen K-edge and niobium L-edge of native niobium films were investigated (both the aluminum and niobium films were covered with amorphous thermal oxide due to exposure to atmosphere).
- the samples were cooled down to 10 K in ultrahigh vacuum, no evidence of magnetism at any of the absorption edges was observed.
- 10 ⁇ 5 Torr of air was introduced into the sample chamber for one minute while the samples were cold, it was found that the oxygen K-edge spectrum changed dramatically, and a large XMCD signal appeared, as illustrated in FIGS. 5 and 6 . Specifically, FIG.
- FIG. 5 shows the appearance of an oxygen K-edge signal in the absorption spectra of an air-dosed aluminum thin film obtained using a total electron yield (“TEY”) mode.
- TEY total electron yield
- a peak around 531 eV develops when the sample is cooled below 50 K.
- a strong signal at the oxygen K-edge can be observed indicating the presence of an adsorbed layer of oxygen on the thin film surface.
- Similar results may be observed in the X-ray absorption spectra using a total fluorescence yield (“TFY”) mode ( FIG. 6 ).
- Density functional theory calculations assigned the measured XMCD signal to molecular oxygen which is known to be magnetically active and exhibit long-range magnetic order in the low-temperature, low-pressure regime relevant to superconducting qubit applications.
- the data support an early speculation that reduced levels of flux noise seen in nitride-encapsulated SQUIDs were due to the fact that the magnetic moment of oxygen has a much higher energy barrier to reorientation on a nitride surface than on an oxide surface, so that adsorbed oxygen would remain magnetically active on conventional oxide-encapsulated devices, but not on nitride-encapsulated devices.
- the inventors showed that the magnetic signature of adsorbed air is identical to that of pure oxygen. This may be understood as a consequence of the extremely low solubility of nitrogen in solid molecular oxygen. Significant adsorption of oxygen is observed only below 50 K and only when the background pressure in the cryostat is worse than a few times 10 ⁇ 8 Torr.
- the present disclosure provides a novel approach to control the proximate environment of the devices prior to and/or during operation of such circuits or devices.
- FIG. 7 shows the temperature dependence of flux in a SQUID device before and after exposure to ammonia gas for a cooling field of ⁇ 256 microTesla.
- the data shows about a three times reduction in the surface spin density after ammonia exposure.
- FIG. 8 shows the temperature dependence of flux in a SQUID device subjected to various ultraviolet exposure conditions compared to air exposure.
- the device was irradiated with ultraviolet light at different wavelengths, namely 275 nm, and 365 nm, while cooling down from room temperature to 3 K.
- About 30% decrease in spin density is observed after ultraviolet exposure, suggesting that ultraviolet light provides energy, which is unfavorable for the surface adsorption process.
- FIG. 9 shows flux versus temperature curves for a device using three different ultraviolet light powers. No significant change in spin density was observed when the power level was varied from 11 mW to 450 mW.
Abstract
Description
- This invention was made with government support under W911NF-10-1-0494 and W911NF-09-1-0375 awarded by the ARMY/ARO. The government has certain rights in the invention.
- The field of the disclosure is directed to superconducting quantum circuits and devices. More particularly, the disclosure is directed to systems and methods related to quantum information processing and quantum computation.
- Superconducting integrated circuits are finding increased use in a variety of applications. For instance, in the field of quantum computation, the performance of superconducting quantum bits (“qubits”) has advanced rapidly in recent years, with preliminary multi-qubit implementations leading toward scalable, surface code architectures. In contrast to classical computational methods that rely on binary data stored in the form of definite on/off states, or bits, methods in quantum computation take advantage of the quantum mechanical nature of superconducting quantum systems, which may be represented using a superposition of multiple quantum states.
- However, maintaining a superposition state is challenging for practical implementations. This is because various sources of noise induce a loss of quantum ordering, or coherence in the phase angles between the different components of the system in quantum superposition. Such dephasing makes the realization of quantum computers difficult, since sufficient preservation of coherent quantum states is required in order to perform useful computation. For superconducting qubits, low-frequency magnetic flux noise is a dominant source of dephasing, resulting in appreciable errors when implemented in large-scale circuits. In addition, the magnitude of flux noise is roughly universal across various different device materials and fabrication processes. Despite thirty years of research, there has been no successful demonstration of reducing this noise, placing severe limitations on progress in quantum information processing and quantum computation.
- In general, during the fabrication process, superconducting devices are exposed to ambient atmospheric surroundings for extended periods of time. Subsequently, in operation, the superconducting devices are cooled to low temperatures, typically using vacuum cryostats that maintain poor background pressure, allowing the adsorption of a high density of magnetically active defects. Such defects can produce low-frequency magnetic flux noise that leads to strong dephasing. In the case of qubit devices, some efforts to avoid magnetic flux noise have been made by operating the devices at fixed frequencies where the qubit is insensitive to first order to magnetic flux fluctuations. However, such implementations severely constrain the architectures of multi-qubit circuits and make scaling to larger systems a major challenge.
- In light of the above, there remains a need for novel approaches that address noise sources affecting superconducting integrated circuits.
- The present disclosure introduces a novel approach for controlling noise in superconducting quantum circuits that overcomes the drawbacks of previous technologies. Specifically, the present disclosure recognizes that dominant sources of noise can arrive via molecular species found in ambient surroundings, rather than inherently from materials and geometries utilized therein. For instance, molecular oxygen is a magnetically active species that exhibits long range magnetic order at low temperatures and pressures. Adsorption of molecular oxygen can lead to appreciable magnetic noise in superconducting quantum circuits, such as superconducting qubits. Therefore, in accordance with the present invention, provided systems and methods are directed to controlling the proximate environment of superconducting quantum circuits. By suppressing surface effects, such as magnetically active defects, sources of noise can be appreciably reduced or eliminated.
- In accordance with one aspect of the present disclosure, a method for reducing magnetic noise in qubit circuits is provided. The method includes providing one or more qubit circuits, and arranging the one or more qubit circuits in a hermetic enclosure capable of isolating the one or more qubit circuits from ambient surroundings. The method also includes controlling a background pressure of one or more magnetically active species in the hermetic enclosure to suppress magnetically active surface defects associated with the one or more qubit circuits.
- In accordance with another aspect of the present disclosure, a system for suppressing magnetically active surface defects in superconducting quantum circuits is provided. The system includes a hermetic enclosure configured to accommodate therein one or more superconducting quantum circuits, and capable of isolating the one or more superconducting circuits from ambient surroundings. The system also includes a vacuum system removably coupled to the hermetic enclosure, and configured to control an environment in the hermetic enclosure such that magnetically active surface defects associated with the one or more superconducting quantum circuits are suppressed.
- In accordance with yet another aspect of the present disclosure, a method for suppressing magnetically active surface defects in superconducting quantum circuits is provided. The method includes providing one or more superconducting quantum circuits, and arranging the one or more superconducting quantum circuits in a hermetic enclosure. The method also includes controlling an environment in the hermetic enclosure to suppress magnetically active surface defects associated with the one or more superconducting quantum circuits.
- The foregoing and other aspects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings that form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims and herein for interpreting the scope of the invention.
-
FIG. 1 shows a flowchart setting forth steps of a method in accordance with the present disclosure. -
FIG. 2 shows another flowchart setting forth steps of a method in accordance with the present disclosure. -
FIG. 3A shows an example hermetic enclosure in accordance with aspects of the present disclosure. -
FIG. 3B shows an example of vacuum enclosure for use in coating the surfaces of superconducting circuits with non-magnetic encapsulation layers to prevent subsequent adsorption of magnetically active defects, in accordance with aspects of the present disclosure. -
FIG. 4 is a graph showing oxygen x-ray magnetic circular dichroism (“XMCD”) signal for thin film air-dosed aluminum as a function of magnetic field at 10 Kelvin. -
FIG. 5 is a graph of X-ray absorption spectra for thin film air-dosed aluminum indicating the presence of adsorbed molecular oxygen for temperatures below 50 Kelvin. -
FIG. 6 is another graph of X-ray absorption spectra for thin film air-dosed aluminum indicating the presence of adsorbed molecular oxygen for temperatures below 50 Kelvin. -
FIG. 7 is a graph illustrating the effect of ammonia exposure on a superconducting quantum interference device (“SQUID”). -
FIG. 8 is a graph illustrating the effect of ultraviolet light exposure on a SQUID. -
FIG. 9 is a graph illustrating the effect of ultraviolet light power on a SQUID. - Surface effects, such as magnetically active defects, can represent significant sources of noise that can impede or limit the functionality of certain superconducting devices. For example, recent investigations by the inventors demonstrated that the dominant contribution to magnetic flux noise observable in superconducting quantum bit (“qubit”) devices originated from oxygen-containing adsorbates that produced a high density of magnetically active defects at the surface of superconducting devices. Such low-frequency magnetic flux noise represents a dominant source of dephasing, a key figure of merit for superconducting qubit operation.
- Therefore, the present disclosure describes systems and methods directed to controlling the environment of superconducting quantum circuits for purposes including mitigating potential sources of noise, such as magnetic noise, found therein. For instance, as will be described, the density of surface defects, such as magnetically active surface defects, may reduced by limiting or prevention exposure to, and/or inducing desorption of active adsorbates, such as oxygen-containing adsorbates.
- Turning to
FIG. 1 , a flowchart setting forth steps of aprocess 100 in accordance with aspects of the present disclosure is shown. Theprocess 100 may begin atprocess block 102 where one or more superconducting quantum circuit(s), such as qubit circuits, may be provided. In some aspects, the one or more superconducting quantum circuit(s) may be fabricated atprocess block 102 in accordance with standard device practice. In some designs, the surface of the superconducting quantum circuit(s) may be coated with a non-magnetic encapsulation layer. This may be advantageous particularly to devices that are sensitive to magnetically active defects and magnetic noise. By way of example, candidate materials can include waxes, similar to the etch resist Apiezon W, with layer thicknesses on the order of millimeters, although other materials and layer thickness may be possible. - At
process block 104, the superconducting quantum circuit(s) may then be arranged or positioned in a hermetic enclosure configured to accommodate therein one or more superconducting quantum circuits. As will be described, the sealable hermetic enclosure can be configured in any manner, and capable of a range of functionality, including isolating the superconducting quantum circuit(s) from ambient surroundings. - Then, as indicated by
process block 106, the environment in the hermetic enclosure may be controlled, for instance, in a manner such that magnetically active surface defects in the superconducting quantum circuit(s) are suppressed. In some aspects, this step can include generating a vacuum or near-vacuum environment, for instance, by operating a vacuum system coupled to the hermetic enclosure. - In some modes of operation, the vacuum system may be capable of controlling the background pressure of the hermetic enclosure such that high vacuum or ultrahigh vacuum conditions are achieved. By way example, a high vacuum can be in a pressure range roughly between 10−6 to 10−8 Torr, and ultrahigh vacuum can be in a range of 10−8 Torr or lower, although other pressure values may be possible. In some aspects, the temperature of the hermetic enclosure may be elevated while reducing the pressure therein in order to bake out, or desorb, and subsequently remove active adsorbates or contaminants present in or about the enclosure walls. In some aspects, the native surface of the superconducting circuits can be passivated or modified at
process block 106, for example, by backfilling, or pressurizing, the hermetic enclosure after evacuation with an inert or nonmagnetic gas, such as ammonia gas. In addition, the surface of the superconducting circuits can also be irradiated using light atprocess block 106, for instance, while performing a device cool-down protocol in order to promote photodesorption of active adsorbates. By way of example, ultraviolet light may be used to irradiate the superconducting circuit(s). - Performing any combination of the steps detailed with respect to process block 106, the density of one or more active species, such as magnetically active species, may be controlled such that sources of noise can be appreciably reduced. In particular, any such steps can be applied to the superconducting quantum circuit(s) or portions thereof that are sensitive to noise and dephasing, and are particularly relevant to large-scale multi-qubit circuits for gate-based quantum computing or quantum annealing.
- Turning to
FIG. 2 , another flowchart setting forth steps of aprocess 200 in accordance with aspects of the present disclosure is shown. Theprocess 200 may begin at process block 202 where one or more qubit circuit(s) or devices are arranged or positioned in a hermetic enclosure. - At
process block 204, the environment in the hermetic enclosure may be controlled by reducing background pressure to obtain a target coverage, or lack thereof, of magnetic, as well as other undesirable adsorbates, on the surface of the qubit circuit(s). As described, this can be achieved by evacuating the hermetic enclosure to a high or ultrahigh vacuum, while optionally baking out the enclosure. In some aspects, as indicated byprocess block 206, evacuation may also be followed by backfilling the enclosure with inert gases in order to occupy available adsorption sites at the surface of the qubit circuit(s), thus preventing the adsorption of residual magnetically active species, such as molecular oxygen. By way of example, ammonia gas may be a suitable candidate for passivating a device surface such that magnetically active surface defects are suppressed, although other gases are also possible. - At
process block 208, the qubit circuit(s) may then be operated with a suppressed density of surface defects. As described, qubit circuit(s) may particularly benefit from a reduced density of magnetically active surface defects that would reduce sources of noise, decoherence and dephasing. In some aspects, further control in the density of magnetically active adsorbed defects can include irradiation of the qubit circuit(s) in the hermetic enclosure with light, such as ultraviolet light, either during the evacuation process atprocess block 204, and/or during a cool down process associated with operation atprocess block 208. - In accordance with aspects of the present disclosure, a system for suppressing magnetically active surface defects in superconducting quantum circuits is provided. The system can include a hermetic enclosure configured to accommodate therein at least one or more superconducting quantum circuits, such as qubit circuits, and a vacuum system removably coupled to the hermetic enclosure, and configured to control an environment in the hermetic enclosure such that surface defects, such as magnetically active surface defects, associated with the superconducting quantum circuits are suppressed.
- The hermetic enclosure can be designed in any manner, and include capabilities for controlling and operating devices, circuits or circuit components, including superconducting quantum circuits, arranged therein. Specifically, the hermetic enclosure may be capable of isolating such devices, circuits or circuit components from ambient surroundings. This may be implemented using various features or elements suitable for achieving and sustaining vacuum or near-vacuum conditions, pressurized conditions, low-temperature conditions, and so forth. For instance, in some implementations, the hermetic enclosure may contain all-metal seals, such as conflat gaskets, and be constructed from welded aluminum with aluminum-stainless steel bimetal flanges for the vacuum seals, or may be constructed from an alloy of titanium machined to form knife edges for use in producing vacuum seals. However, the hermetic enclosure may be constructed in other ways as well.
- Other functionalities of the hermetic enclosure include, for instance, configurations for mitigating, reducing or eliminating sources of noise found in ambient surroundings, such as thermal, electrical, and magnetic sources of noise, and other sources of noise. Also, the hermetic enclosure may configured to include or accommodate a heat source for elevating a temperature of the hermetic enclosure, for example, during an evacuation process. The hermetic enclosure may also include a light source, such as an LED device, capable of irradiating devices, circuits or circuit components therein using light, such as ultraviolet light. For instance, the light source may be operated during a cooling procedure, such that active species present on the surface of the superconducting circuits are desorbed.
- By way of example,
FIG. 3A shows an examplehermetic enclosure 300 in accordance with aspects of the present disclosure. As illustrated, thehermetic enclosure 300 may be constructed using afirst enclosing portion 302 andsecond enclosing portion 304, which when coupled together via a metallic seal, or other seal, can provide vacuum-tight enclosure. Thehermetic enclosure 300 is shown to include a number ofelectrical feedthroughs 306 connectable to circuits arranged therein, although it may be appreciated that other types of feedthroughs are possible. The hermetic enclosure also includes asealable evacuation port 308 configured to be coupled to the vacuum system such that environment in thehermetic enclosure 300 can be controlled. - The
hermetic enclosure 300 may be manufactured using any materials suitable for controlling an environment therein. By way of example, the hermetic enclosure may be fabricated from grade 5 titanium alloy (Ti—6Al—4V), with the following advantageous properties: 1) the material is hard enough to form an ultrahigh vacuum conflat seal; 2) the material is known for its low outgassing and is compatible with the desired ultrahigh vacuum environment; 3) there are commercially available weld-in hermetic wiring feedthroughs, for example of the SMA type, enabling high-bandwidth electrical connections into an ultrahigh vacuum environment; 4) Grade 5 titanium is a nonmagnetic material that is superconducting at low temperatures. This provides magnetic shielding for circuits or devices assembled in thehermetic enclosure 300 that are sensitive to external magnetic field fluctuations. - The vacuum system (not shown in
FIG. 3A ) may be configured to control a background pressure of one or more active species in thehermetic enclosure 300, such as magnetically active species like molecular oxygen. As described, this may be achieved by evacuating thehermetic enclosure 300 to a high or ultrahigh vacuum, and optionally baking out thehermetic enclosure 300 using a heat source. - In some aspects, the vacuum system may be configured to introduce inert gases into the
hermetic enclosure 300 in order to passivate active surface defects of the superconducting circuits therein, the inert gas occupying available adsorption sites. For example, ammonia gas may be utilized, although other gases may also be possible. In the case of qubit circuits, this would prevent surface adsorption of residual magnetically active species, such as molecular oxygen, and hence further suppress sources of qubit decoherence and dephasing. - Turning to
FIG. 3B , an example ofvacuum enclosure 350, for use in coating the surfaces of superconducting circuits with non-magnetic encapsulation layers, is shown. Such encapsulation layers would prevent adsorption of magnetically active defects found in close proximity to the superconducting circuits, where coupling to the surface defects is strong. By way of example, non-magnetic encapsulation materials for use in thevacuum enclosure 350 may include etch resist waxes, such as Apiezon W, or UHV-compatible epoxies, such as Torr Seal or Epo-tek, but other encapsulation materials are possible. - The
vacuum enclosure 350 may include a broad range of functionality, including capabilities for controlling an environment therein, for instance, by reducing ambient pressure to achieve vacuum or near vacuum conditions, or a targeted background pressure. In addition, thevacuum enclosure 350 may be configured with capabilities to dispense or deposit non-magnetic encapsulation layers upon surfaces of superconducting circuits therein. As shown in the example ofFIG. 3B , thevacuum enclosure 350 can include aninlet 352 configured to dispense non-magnetic encapsulation layers using a dispensingtube 354. However, it may be appreciated, however, that other methods for coating the surface of a device inside thevacuum enclosure 350, using a non-magnetic encapsulation layer, may be possible. Following vacuum encapsulation, the device can be exposed to atmosphere, as well as cooled to low temperatures in a non-hermetic enclosure, without appreciably deleterious consequences, since any magnetically active defects would be prevented from adsorbing in close proximity to the device. - Low-
frequency 1/f flux noise is a dominant source of dephasing in superconducting Josephson qubits. While it is possible to avoid flux noise by replacing SQUID loops with single junctions or by operating the qubit at a so-called flux “sweet spot,” where the device is insensitive to first order to magnetic flux fluctuations, such strategies severely constrain qubit gates, and hence overall architectures, since such limited qubits would no longer be tunable. In previous investigations by the inventors, it was demonstrated that there exists a high density of unpaired magnetic defect states in the surfaces of superconducting thin films, and it is believed that such defects are the source of the ubiquitous 1/f flux noise. Therefore, systems and methods, in accordance with aspects of the present disclosure, can be used to reduce 1/f flux noise by controlling the environment proximate to qubit devices, such that magnetically active surface defects are suppressed. - In experiments involving an X-ray Magnetic Circular Dichroism (“XMCD”) technique, native superconducting thin film samples were irradiated with left and right circularly polarized x-rays, and the differences in absorption spectra at various x-ray edges were examined. By way of example,
FIG. 4 shows a graph of oxygen XMCD signal for thin film air-dosed aluminum as a function of magnetic field at 10 Kelvin. Differences in x-ray absorption for the opposite x-ray helicities reveal the orbital, and in some cases spin, polarization of the hole states to which the photoelectrons are promoted. Oxygen and aluminum K-edges of native aluminum films, and the oxygen K-edge and niobium L-edge of native niobium films were investigated (both the aluminum and niobium films were covered with amorphous thermal oxide due to exposure to atmosphere). When the samples were cooled down to 10 K in ultrahigh vacuum, no evidence of magnetism at any of the absorption edges was observed. However, when 10−5 Torr of air was introduced into the sample chamber for one minute while the samples were cold, it was found that the oxygen K-edge spectrum changed dramatically, and a large XMCD signal appeared, as illustrated inFIGS. 5 and 6 . Specifically,FIG. 5 shows the appearance of an oxygen K-edge signal in the absorption spectra of an air-dosed aluminum thin film obtained using a total electron yield (“TEY”) mode. A peak around 531 eV develops when the sample is cooled below 50 K. At 10 K, a strong signal at the oxygen K-edge can be observed indicating the presence of an adsorbed layer of oxygen on the thin film surface. Similar results may be observed in the X-ray absorption spectra using a total fluorescence yield (“TFY”) mode (FIG. 6 ). - Density functional theory calculations assigned the measured XMCD signal to molecular oxygen, which is known to be magnetically active and exhibit long-range magnetic order in the low-temperature, low-pressure regime relevant to superconducting qubit applications. Moreover, the data support an early speculation that reduced levels of flux noise seen in nitride-encapsulated SQUIDs were due to the fact that the magnetic moment of oxygen has a much higher energy barrier to reorientation on a nitride surface than on an oxide surface, so that adsorbed oxygen would remain magnetically active on conventional oxide-encapsulated devices, but not on nitride-encapsulated devices. In other experiments, the inventors showed that the magnetic signature of adsorbed air is identical to that of pure oxygen. This may be understood as a consequence of the extremely low solubility of nitrogen in solid molecular oxygen. Significant adsorption of oxygen is observed only below 50 K and only when the background pressure in the cryostat is worse than a
few times 10−8 Torr. - In recognizing that dominant sources of noise in superconducting quantum circuits or devices need not be intrinsic to the materials and geometries utilized, but rather originating from active species present under ambient conditions, the present disclosure provides a novel approach to control the proximate environment of the devices prior to and/or during operation of such circuits or devices.
- As described, this can include generating vacuum or near-vacuum conditions in a hermetic enclosure housing the circuits or devices, as well as pressurizing the enclosure with an inert gas. By way of example,
FIG. 7 shows the temperature dependence of flux in a SQUID device before and after exposure to ammonia gas for a cooling field of ±256 microTesla. The data shows about a three times reduction in the surface spin density after ammonia exposure. - In addition, suppressing active surface defects, in accordance with the present disclosure, can be achieved by exposure to light, such as ultraviolet light. By way of example,
FIG. 8 shows the temperature dependence of flux in a SQUID device subjected to various ultraviolet exposure conditions compared to air exposure. The device was irradiated with ultraviolet light at different wavelengths, namely 275 nm, and 365 nm, while cooling down from room temperature to 3 K. About 30% decrease in spin density is observed after ultraviolet exposure, suggesting that ultraviolet light provides energy, which is unfavorable for the surface adsorption process. Similarly,FIG. 9 shows flux versus temperature curves for a device using three different ultraviolet light powers. No significant change in spin density was observed when the power level was varied from 11 mW to 450 mW. - The present invention has been described in terms of one or more preferred embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly stated, are possible and within the scope of the invention.
Claims (28)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/632,505 US9437800B1 (en) | 2015-02-26 | 2015-02-26 | Systems and methods for suppressing magnetically active surface defects in superconducting circuits |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/632,505 US9437800B1 (en) | 2015-02-26 | 2015-02-26 | Systems and methods for suppressing magnetically active surface defects in superconducting circuits |
Publications (2)
Publication Number | Publication Date |
---|---|
US20160254434A1 true US20160254434A1 (en) | 2016-09-01 |
US9437800B1 US9437800B1 (en) | 2016-09-06 |
Family
ID=56799170
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/632,505 Active US9437800B1 (en) | 2015-02-26 | 2015-02-26 | Systems and methods for suppressing magnetically active surface defects in superconducting circuits |
Country Status (1)
Country | Link |
---|---|
US (1) | US9437800B1 (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10769546B1 (en) * | 2015-04-27 | 2020-09-08 | Rigetti & Co, Inc. | Microwave integrated quantum circuits with cap wafer and methods for making the same |
CN111882068A (en) * | 2020-06-29 | 2020-11-03 | 北京百度网讯科技有限公司 | Method, device, equipment and medium for eliminating noise influence of QOA quantum circuit |
US11011693B2 (en) * | 2019-06-24 | 2021-05-18 | Intel Corporation | Integrated quantum circuit assemblies for cooling apparatus |
WO2021094320A1 (en) * | 2019-11-12 | 2021-05-20 | International Business Machines Corporation | Adhesion layer to enhance encapsulation of superconducting devices |
US11121301B1 (en) | 2017-06-19 | 2021-09-14 | Rigetti & Co, Inc. | Microwave integrated quantum circuits with cap wafers and their methods of manufacture |
US11145801B2 (en) | 2019-11-12 | 2021-10-12 | International Business Machines Corporation | Adhesion layer to enhance encapsulation of superconducting devices |
US11158782B2 (en) | 2019-11-12 | 2021-10-26 | International Business Machines Corporation | Metal fluoride encapsulation of superconducting devices |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11348025B2 (en) | 2016-12-29 | 2022-05-31 | Google Llc | Selective capping to reduce quantum bit dephasing |
-
2015
- 2015-02-26 US US14/632,505 patent/US9437800B1/en active Active
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10769546B1 (en) * | 2015-04-27 | 2020-09-08 | Rigetti & Co, Inc. | Microwave integrated quantum circuits with cap wafer and methods for making the same |
US11574230B1 (en) | 2015-04-27 | 2023-02-07 | Rigetti & Co, Llc | Microwave integrated quantum circuits with vias and methods for making the same |
US11121301B1 (en) | 2017-06-19 | 2021-09-14 | Rigetti & Co, Inc. | Microwave integrated quantum circuits with cap wafers and their methods of manufacture |
US11770982B1 (en) | 2017-06-19 | 2023-09-26 | Rigetti & Co, Llc | Microwave integrated quantum circuits with cap wafers and their methods of manufacture |
US11011693B2 (en) * | 2019-06-24 | 2021-05-18 | Intel Corporation | Integrated quantum circuit assemblies for cooling apparatus |
WO2021094320A1 (en) * | 2019-11-12 | 2021-05-20 | International Business Machines Corporation | Adhesion layer to enhance encapsulation of superconducting devices |
US11145801B2 (en) | 2019-11-12 | 2021-10-12 | International Business Machines Corporation | Adhesion layer to enhance encapsulation of superconducting devices |
US11158782B2 (en) | 2019-11-12 | 2021-10-26 | International Business Machines Corporation | Metal fluoride encapsulation of superconducting devices |
CN114631229A (en) * | 2019-11-12 | 2022-06-14 | 国际商业机器公司 | Adhesion layer for enhancing encapsulation of superconducting devices |
US11805707B2 (en) | 2019-11-12 | 2023-10-31 | International Business Machines Corporation | Metal fluoride encapsulation of superconducting devices |
CN111882068A (en) * | 2020-06-29 | 2020-11-03 | 北京百度网讯科技有限公司 | Method, device, equipment and medium for eliminating noise influence of QOA quantum circuit |
Also Published As
Publication number | Publication date |
---|---|
US9437800B1 (en) | 2016-09-06 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US9437800B1 (en) | Systems and methods for suppressing magnetically active surface defects in superconducting circuits | |
Kumar et al. | Origin and reduction of 1/f magnetic flux noise in superconducting devices | |
Grassellino et al. | Unprecedented quality factors at accelerating gradients up to 45 MVm− 1 in niobium superconducting resonators via low temperature nitrogen infusion | |
Dhakal et al. | Effect of high temperature heat treatments on the quality factor of a large-grain superconducting radio-frequency niobium cavity | |
Staunton et al. | Long-range chemical order effects upon the magnetic anisotropy of FePt alloys from an ab initio electronic structure theory | |
KR101862632B1 (en) | Production method and production system for magnetoresistance element | |
Capece et al. | Effects of temperature and surface contamination on D retention in ultrathin Li films on TZM | |
JP2008091484A (en) | Method and device for manufacturing magnetoresistive effect element | |
US11464102B2 (en) | Methods and systems for treatment of superconducting materials to improve low field performance | |
Thomas et al. | Oxidation states of GaAs surface and their effects on neutral beam etching during nanopillar fabrication | |
JP2022525617A (en) | Methods and equipment for depositing multi-layer devices with superconducting membranes | |
Chen et al. | Tracing the origin of oxygen for La0. 6Sr0. 4MnO3 thin film growth by pulsed laser deposition | |
JP6586328B2 (en) | Method for processing an object | |
Morenzoni | Physics and applications of low energy muons | |
JP2022525635A (en) | Methods and equipment for depositing metal nitrides | |
Gurovich et al. | Controlled modification of superconducting properties of NbN ultrathin films under composite ion beam irradiation | |
Konomi et al. | Trial of nitrogen infusion and nitrogen doping by using J-PARC furnace | |
US5282903A (en) | High quality oxide films on substrates | |
Drbohlav et al. | Static SIMS study of Ti, Zr, V and Ti–Zr–V NEG activation | |
Fang et al. | Cryogenic secondary electron yield measurements on structural materials applied in particle accelerators | |
Watson | Growth of low disorder GaAs/AlGaAs heterostructures by molecular beam epitaxy for the study of correlated electron phases in two dimensions | |
Dubyk et al. | Correlation between the atomic and electronic structures in Dy/Mo (1 1 2) and Gd/Mo (1 1 2) adsystems | |
JP2019068012A (en) | Workpiece processing method | |
CN108511389A (en) | Semiconductor making method and plasma processing apparatus | |
Velthaus et al. | Mitigation of ion-induced desorption for accelerator components by surface treatment and annealing |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: WISCONSIN ALUMNI RESEARCH FOUNDATION, WISCONSIN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MCDERMOTT, ROBERT;KUMAR, PRADEEP;REEL/FRAME:035322/0079 Effective date: 20150311 |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
CC | Certificate of correction | ||
FEPP | Fee payment procedure |
Free format text: ENTITY STATUS SET TO UNDISCOUNTED (ORIGINAL EVENT CODE: BIG.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 4TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1551); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Year of fee payment: 4 |
|
FEPP | Fee payment procedure |
Free format text: ENTITY STATUS SET TO SMALL (ORIGINAL EVENT CODE: SMAL); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YR, SMALL ENTITY (ORIGINAL EVENT CODE: M2552); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY Year of fee payment: 8 |