QND measurement of a superconducting qubit in the weakly projective regime

Abstract

Quantum state detectors based on switching of hysteretic Josephson junctions biased close to their critical current are simple to use but have strong back-action. We show that the back-action of a DC-switching detector can be considerably reduced by limiting the switching voltage and using a fast cryogenic amplifier, such that a single readout can be completed within 25 ns at a repetition rate of 1 MHz without loss of contrast. Based on a sequence of two successive readouts we show that the measurement has a clear quantum non-demolition character, with a QND fidelity of 75 %.

submitted to PRL

References in corpus (1)

• Progressive field-state collapse and quantum non-demolition photon counting

Cited by in corpus (10)

• Atomic physics and quantum optics using superconducting circuits
• The Fermi problem with artificial atoms in circuit QED
• Generalized partial measurements
• A quantum no-reflection theorem and the speeding up of Grover's search algorithm
• Detecting ground state qubit self-excitations in circuit QED: slow quantum anti-Zeno effect
• Improved superconducting qubit state readout by path interference
• Short-time quantum detection: probing quantum fluctuations
• Ideal Quantum non-demolishing measurement of a flux qubit at variable bias
• Assessing the quantumness of the annealing dynamics via Leggett Gargs inequalities: a weak measurement approach
• Bipartite entanglement of localized separated systems