Patent ID: 10013657

Abstract:
Method and circuit for reading a value {circumflex over (σ)}z stored in a quantum information unit (qubit) memory having a qubit frequency ωa, with a resonator defined by a resonator damping rate κ, a resonator frequency ωr, a resonator electromagnetic field characterized by â† and â, a longitudinal coupling strength gz, an output âout and a longitudinal coupling gz{circumflex over (σ)}z(â†+â). At a quantum non-demolition (QND) longitudinal modulator, periodically modulating the longitudinal coupling strength gz with a signal of amplitude {tilde over (g)}z at least three (3) times greater than the resonator damping rate κ and of frequency ωm with ωm+κ resonant with ωr, wherein the longitudinal coupling strength gz varies over time (t) in accordance with gz(t)=gz+{tilde over (g)}z cos(ωmt) with gz representing an average value of gz and at a QND homodyne detector, measuring the value {circumflex over (σ)}z of the qubit memory from a phase reading of the output {circumflex over (σ)}out.