Socpra Sciences Et Genie S.e.c.

Jerome Bourassa

Alexandre Blais

Nicloas Didier

Method and circuit for reading a value {circumflex over (&#x3c3;)}stored in a quantum information unit (qubit) memory having a qubit frequency &#x3c9;, with a resonator defined by a resonator damping rate &#x3ba;, a resonator frequency &#x3c9;, a resonator electromagnetic field characterized by &#xe2;and &#xe2;, a longitudinal coupling strength g, an output &#xe2;and a longitudinal coupling g{circumflex over (&#x3c3;)}(&#xe2;+&#xe2;). At a quantum non-demolition (QND) longitudinal modulator, periodically modulating the longitudinal coupling strength gwith a signal of amplitude {tilde over (g)}at least three (3) times greater than the resonator damping rate &#x3ba; and of frequency &#x3c9;with &#x3c9;+&#x3ba; resonant with &#x3c9;, wherein the longitudinal coupling strength gvaries over time (t) in accordance with g(t)=+{tilde over (g)}cos(&#x3c9;t) withrepresenting an average value of gand at a QND homodyne detector, measuring the value {circumflex over (&#x3c3;)}of the qubit memory from a phase reading of the output {circumflex over (&#x3c3;)}.

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Sherbrooke, Canada

Jerome Bourassa