Abstract: Error correction can only work with superconducting qubits if qubit errors are lowered. Surface loss from thin oxides is currently a dominant error mechanism. Formulas for useful qubit geometries are presented to predict surface loss, which can be used to optimize the qubit layout. A significant fraction of surface loss comes from the small wire that connects the Josephson junction to the qubit capacitor. Tapering this wire is shown to significantly lower its loss, as well as etching the underlying silicon to create free-standing wires.

Abstract: Large algorithms can be run on a quantum computer only if quantum error correction is used to lower logical qubit errors. The energy deposited by cosmic-ray muons produces a quasiparticle “heat” pulse that causes the qubits to decay in energy quickly, with errors correlated in space and time, so that error correction fails. Metal layers comprising normal metal and/or small-gap superconductors channel this energy away from the qubit into benign structures so that qubit performance is not degraded. These structures are designed according to the electron-phonon interactions and constraints from electromagnetic radiation to make large reductions in the induced errors so that error correction works properly.

Abstract: Multi-layer transition-edge sensors (TES) having improved performance, a method for preparing them and methods of using them. Specifically, the improvement lies in providing normal metal strips along the edges of the superconducting and normal metal layers parallel to the current flow in the TES during operation. These strips (referred to as “banks”) provide for both improved detector performance and improved detector robustness against corrosion. This improvement is an important advance particularly for TES-based microcalorimeter detectors. The improved TESs also have many other applications based on the very precise thermometer function achieved by the TES.

Abstract: This invention provides a mechanical support for a two-pill Adiabatic Demagnetization Refrigerator (ADR). The support utilizes a suspension of the two pills from one side of the magnet bore only. In the two pill ADR, the thermal ground is at 4K, a guard pill positioned in the front of the bore cools to 1K and a base pill positioned in the back of the bore cools to 50-100 mk. A connector rod of the base pill traverses the guard pill, and connector rods to both the guard pill and base pill exit through the front aperture. A preferred embodiment of the two-pill support for the front loaded magnet bore utilizes planar support modules comprising three members connected by Kevlar strings. Each member is thermally connected either to one of the pills or to thermal ground. The ground member, the guard member and the base member of the support module are strung with Kevlar threads, such that the base member is suspended only from the guard member, and the guard member only from the ground member.

Abstract: This invention provides a method and apparatus for particle detection utilizing an Al/normal-metal bilayer transition-edge sensor (TES) coupled with a particle absorber. The TES is maintained in the transition region where its properties are extremely sensitive to temperature. In the detector, the energy of an absorbed particle is converted to heat by the absorber and the transition from the bilayer's superconducting to normal state is used to sense the temperature rise. The transition temperature, T.sub.c, of the bilayer can be reproducibly controlled as a function of the relative thicknesses and the total thickness of the superconducting and normal-metal layers. The range of available T.sub.c 's extends from below 50 mK to above 1 K, allowing the detector to be tailored to the application. For x-ray detection the preferred T.sub.c is about 50-150 mK. The width of the transition edge can be less than 0.1 mK, which allows very high detector sensitivity.

Abstract: A low noise radiofrequency amplifier (10), using a dc SQUID (superconducting quantum interference device) as the input amplifying element. The dc SQUID (11) and an input coil (12) are maintained at superconductivity temperatures in a superconducting shield (13), with the input coil (12) inductively coupled to the superconducting ring (17) of the dc SQUID (11). A radiofrequency signal from outside the shield (13) is applied to the input coil (12), and an amplified radiofrequency signal is developed across the dc SQUID ring (17) and transmitted to exteriorly of the shield (13). A power gain of 19.5.+-.0.5 dB has been achieved with a noise temperature of 1.0.+-.0.4 K. at a frequency of 100 MHz.