University System of Maryland

United States of America As Represented by the Secretary of the Air Force

The United States of America, As Represented by the Director, National Security Agency

National Security Agency

Frederick Charles Wellstood

John Matthews

Steven Mark Anlage

Kosta P Vlahacos

Erin F Fleet

Steven M Green

Sojiphong Chatraphorn

David Ethan Steinhauer

Soun Pil Kwon

Randall C Black

Dian Song

Claudio Felipe Busko

Randall Christopher Black

Yonggyu Gim

Jay LeFebvre

Constantine P Vlahacos

Anna Mathai

Jen-Hao Yeh

Su-Young Lee

David E Steinhauer

Benjamin S Palmer

Matthew Edward Kenyon

Christopher J Lobb

A dissipative device has a planar configuration with one or more resistor elements formed on an insulating substrate. Conductors are formed on the insulating substrate and are coupled to the resistor element(s) to transmit signals to/from the resistor element(s). The geometry of and materials for the dissipative device allow the conductors to act as heat sinks, which conduct heat generated in the resistor element(s) to the substrate (and on to a coupled housing) and cool hot electrons generated by the resistor element(s) via electron-phonon coupling. The dissipative device can be used in cooling a signal to a qubit, a cavity system of a quantum superconducting qubit, or any other cryogenic device sensitive to thermal noise.

Low-noise, ultra-low temperature dissipative devices

A scanning SQUID microscope is set forth to provide improved output imaging. The SQUID microscope includes a vertically adjustable housing adapted to securely retain a SQUID loop or sensor. A scanning stage of the SQUID microscope is adapted to support a sample while moving the sample along a predetermined path to selectively position predetermined portions of the sample in close proximity to the SQUID loop or sensor to permit the loop or sensor to detect predetermined magnetic field information provided by the predetermined portions of the sample. A position control processor coupled to the scanning stage is operative to receive and process the predetermined magnetic field information to provide corresponding position noise information. Criteria are also presented for determining the expected level of position noise under given experimental conditions.

Scanning SQUID microscope having position noise compensation

A scanning SQUID microscope capable of high frequency magnetic field measurements uses a hysteretic SQUID detector and a pulsed sampling technique which permits to extend the bandwidth of the SQUID microscope to above GHz region. The system can be readily incorporated into a 4.2scanning SQUID microscope for imaging chips at room temperature. By biasing the hysteretic SQUID with pulses of a predetermined amplitude, and adjusting a modulation flux applied to the hysteretic SQUID at a plurality of time delays between the activation of the sample under study and the bias pulse, the hysteretic SQUID can be switched on, and the modulation flux value corresponding to such a switching event as a function of time is considered as representation of the magnetic field emanating from the sample under study.

High frequency scanning SQUID microscope and method of measuring high frequency magnetic fields

A technique for eliminating edge artifacts in magnetic microscopy includes the steps of scanning a SQUID over an object under study to acquire values of magnetic fields produced by currents running in the object to create a first data set having N data points. At the end of the first data set, N zero data points are added to create a second data set having 2N data points. Fast Fourier Transform (FFT) is further applied to the 2N data set to obtain k-space having b(k) values. The b(k) values of the k-space are averaged, and the averaged b(k) values corresponding to k exceeding a predetermined k value are filtered off. A set of current density representations i(k) in the k-space are obtained to which inverse FFT is applied to obtain a map of current densities I(x,y) of the object. A system for performing the method of the present invention includes a software designed to suppress (or eliminate) edge artifacts present in the obtained images.

Method for suppressing edge artifacts in magnetic microscopy

A near-field scanning microwave microscope images the permittivity and dielectric tunability of bulk and thin film dielectric samples on a length scale of about 1 micron or less. The microscope is sensitive to the linear permittivity, as well as to non-linear dielectric terms, which can be measured as a function of an applied electric field. A versatile finite element model is used for the system, which allows quantitive results to e obtained. The technique is non-destructive and has broadband (0.1-50 GHz) capability.

Quantitative imaging of dielectric permittivity and tunability

A method of, an and apparatus for, creating an image of currents flowing through current paths in a microelectronic circuit such that the image of the currents has improved spatial resolution using filters. The filters increase the spatial resolution and eliminate noise and edge artifacts in magnetic field and electric field images of electronic circuits. In accordance with the method, a magnetic field image is created with a scanning SQUID microscope. A magnetic inversion technique is then used to convert the magnetic field image into a current density image. The current density image is filtered based upon known restrictions on the wiring geometry of the microelectronic circuit being imaged. The technique can also be applied to convert electric fields of a circuit from a scanning single electron transistor microscope into images of the voltage levels on the wires in the circuit.

Imaging using spatial frequency filtering and masking

A system, method, and computer program product are provided for scanning objects such as computer chips. A near-field scanning Single Electron Transistor (SET) is used to detect features of the object. In particular, the SET detects variations in an electric field surrounding or emanating from the object. The variation in the field may be associated with an irregularity in the object, such as an open in the circuitry of a chip. In the case of a chip or a multi-chip module, a voltage is applied to the line containing the suspected open. If an actual open is present, the open will be manifested in an irregularity in the electric field associated with the line. The SET detects the irregularity in the field. For the SET to operate, a sufficiently cold operating temperature is maintained for the SET. A very low (cryogenic) temperature allows the use of a larger, more sensitive SET. Scanning SETs are known in the literature, but in such systems the object to be scanned must also be at cryogenic temperatures. In the invention described herein, the object to be scanned can be left at a temperature in its normal environmental temperature range. This temperature range is referred to hereinafter as the ambient temperature range of the object. A chip, for example, typically operates in an ambient temperature range that includes room temperature. Data from the SET indicating irregularity in the electric field can be used to derive readout data, which can in turn be used to produce an image of the object scanned.

Scanning single electron transistor microscope for imaging ambient temperature objects

The microscope includes a microwave generator connected to a mismatched transmission line which terminates in a probe with an exposed end. When a sample is brought into close proximity with the exposed end of the probe, the frequencies and quality factors of the standing wave resonances on the transmission line between the source and the probe are modified. The microwave signal reflected from the end of the probe varies as the capacitance between the probe and the sample changes and as the conductivity of the sample changes. Scanning the sample relative to the probe allows generation of an image from the variation of the reflected signal. Alternatively, to image a device with the microscope, a microwave signal is applied to the device, the probe is scanned over the device, and the signal that is picked up is recorded. In a second embodiment, a first lock-in amplifier is used to lock in the microscope at the resonant frequency, and a second lock-in amplifier is used to detect a curvature of the resonance.

Near-field scanning microwave microscope having a transmission line with

A cryogenic apparatus for microscopy of physical properties of an object including a thin, stiff, transparent substrate or window within the outer wall of the vacuum space of a dewar and a cryogenic sensor within the vacuum space and spaced very close distances to the window. This construction allows for positioning a sample for measurement outside of the vacuum space, at room temperature or higher and for microscopy of physical properties of the sample by monitoring the output from the cryogenic sensor as it is scanned along the surface of the sample.

Apparatus for microscopic imaging of electrical and magnetic properties

A magnetic flux microscope that measures the magnetic field about a sample surface. The apparatus uses a thin-film superconducting quantum interference device (SQUID) as the scanning device. Magnetic shielding is provided about the SQUID and is held stationary relative to the SQUID. The apparatus and method provides a very high magnetic image of the sample with a very high spatial and field resolution.

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Fairfax Station, VA, United States of America

Frederick Charles Wellstood