The QICK (Quantum Instrumentation Control Kit): Readout and control for qubits and detectors.

We introduce a Xilinx RF System-on-Chip (RFSoC)-based qubit controller (called the Quantum Instrumentation Control Kit, or QICK for short), which supports the direct synthesis of control pulses with carrier frequencies of up to 6 GHz. The QICK can control multiple qubits or other quantum devices. The QICK consists of a digital board hosting an RFSoC field-programmable gate array, custom firmware, and software and an optional companion custom-designed analog front-end board. We characterize the analog performance of the system as well as its digital latency, important for quantum error correction and feedback protocols. We benchmark the controller by performing standard characterizations of a transmon qubit. We achieve an average gate fidelity of Favg=99.93%. All of the schematics, firmware, and software are open-source.

Constraints on Scalar Field Dark Matter from Colocated Michelson Interferometers.

Low-mass (sub-eV) scalar field dark matter may induce apparent oscillations of fundamental constants, resulting in corresponding oscillations of the size and the index of refraction of solids. Laser interferometers are highly sensitive to changes in the size and index of refraction of the main beam splitter. Using cross-correlated data of the Fermilab Holometer instrument, which consists of twin colocated 40-m arm length power-recycled interferometers, we investigate the possible existence of scalar field dark matter candidates in the mass range between 1.6×10^{-12} eV and 1.0×10^{-7} eV. We set new upper limits for the coupling parameters of scalar field dark matter, improving on limits from previous direct searches by up to 3 orders of magnitude.

Interferometric Constraints on Spacelike Coherent Rotational Fluctuations.

Precision measurements are reported of the cross-spectrum of rotationally induced differential position displacements in a pair of colocated 39 m long, high-power Michelson interferometers. One arm of each interferometer is bent 90° near its midpoint to obtain sensitivity to rotations about an axis normal to the plane of the instrument. The instrument achieves quantum-limited sensing of spatially correlated signals in a broad frequency band extending beyond the 3.9-MHz inverse light travel time of the apparatus. For stationary signals with bandwidth Δf>10 kHz, the sensitivity to rotation-induced strain h of classical or exotic origin surpasses CSD_{δh}

Second generation readout for large format photon counting microwave kinetic inductance detectors.

We present the development of a second generation digital readout system for photon counting microwave kinetic inductance detector (MKID) arrays operating in the optical and near-infrared wavelength bands. Our system retains much of the core signal processing architecture from the first generation system but with a significantly higher bandwidth, enabling the readout of kilopixel MKID arrays. Each set of readout boards is capable of reading out 1024 MKID pixels multiplexed over 2 GHz of bandwidth; two such units can be placed in parallel to read out a full 2048 pixel microwave feedline over a 4 GHz-8 GHz band. As in the first generation readout, our system is capable of identifying, analyzing, and recording photon detection events in real time with a time resolution of order a few microseconds. Here, we describe the hardware and firmware, and present an analysis of the noise properties of the system. We also present a novel algorithm for efficiently suppressing IQ mixer sidebands to below -30 dBc.

First Measurements of High Frequency Cross-Spectra from a Pair of Large Michelson Interferometers.

Measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of colocated 39 m long, high power Michelson interferometers with flat broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light-crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over 2×10^{8} independent spectral measurements with 381 Hz frequency resolution to obtain 2.1×10^{-20}m/sqrt[Hz] sensitivity to stationary signals. For signal bandwidths Δf>11 kHz, the sensitivity to strain h or shear power spectral density of classical or exotic origin surpasses a milestone PSD_{δh}