Reverse isolation and backaction of the SLUG microwave amplifier

Abstract

An ideal preamplifier for qubit measurement must not only provide high gain and near quantum-limited noise performance, but also isolate the delicate quantum circuit from noisy downstream measurement stages while producing negligible backaction. Here we use a Superconducting Low-inductance Undulatory Galvanometer (SLUG) microwave amplifier to read out a superconducting transmon qubit, and we characterize both reverse isolation and measurement backaction of the SLUG. For appropriate dc bias, the SLUG achieves reverse isolation that is better than that of a commercial cryogenic isolator. Moreover, SLUG backaction is dominated by thermal emission from dissipative elements in the device. When the SLUG is operated in pulsed mode, it is possible to characterize the transmon qubit using a measurement chain that is free from cryogenic isolators or circulators with no measurable degradation of qubit performance.

arXiv comment5 pages, 4 figures

References in corpus (19)

• Surface codes: Towards practical large-scale quantum computation
• Superconducting qubit in waveguide cavity with coherence time approaching 0.1ms
• AC-Stark Shift and Dephasing of a Superconducting Qubit Strongly Coupled to a Cavity Field
• Phase preserving amplification near the quantum limit with a Josephson Ring Modulator
• A widely tunable parametric amplifier based on a SQUID array resonator
• Dephasing of a superconducting qubit induced by photon noise
• Dispersive regime of circuit QED: photon-dependent qubit dephasing and relaxation rates
• Dispersive magnetometry with a quantum limited SQUID parametric amplifier
• Noiseless nonreciprocity in a parametric active device
• The reconfigurable Josephson circulator/directional amplifier
• Photon Shot Noise Dephasing in the Strong-Dispersive Limit of Circuit QED
• On-chip superconducting microwave circulator from synthetic rotation
• Measurement-induced qubit state mixing in circuit QED from up-converted dephasing noise
• Graph-based analysis of nonreciprocity in coupled-mode systems
• Josephson directional amplifier for quantum measurement of superconducting circuits
• Directional amplification with a Josephson circuit
• Superconducting Low-Inductance Undulatory Galvanometer Microwave Amplifier
• High Fidelity Qubit Readout with the Superconducting Low-Inductance Undulatory Galvanometer Microwave Amplifier
• Gain, directionality and noise in microwave SQUID amplifiers: Input-output approach

Cited by in corpus (5)

• High-Fidelity Measurement of a Superconducting Qubit using an On-Chip Microwave Photon Counter
• Efficient qubit measurement with a nonreciprocal microwave amplifier
• Efficient and Low-Backaction Quantum Measurement Using a Chip-Scale Detector
• High-fidelity qubit readout using interferometric directional Josephson devices
• Nonreciprocity in microwave optomechanical circuits