Dresden 2014 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 6: Transport: Quantum Coherence and Quantum Information Systems - Theory I
TT 6.1: Talk
Monday, March 31, 2014, 11:00–11:15, HSZ 204
Efficient Qubit Readout Using Josephson Photomultipliers — •Luke C. G. Govia1, Emily J. Pritchett1,2, Canran Xu3, Maxim G. Vavilov3, Britton L. T. Plourde4, Robert McDermott3, and Frank K. Wilhelm1 — 1Universität des Saarlandes, Saarbrücken, Germany. — 2HRL Laboratories, Malibu, California, USA. — 3University of Wisconsin-Madison, Wisconsin, USA. — 4Syracuse University, New York, USA.
A Josephson Photomultplier (JPM) - a current-biased Josephson junction operated near its critical bias - can absorb and detect weak microwave signals with high sensitivity (PRL 107, 217401 (2011)). When strongly coupled to a high-Q transmission line ``cavity", the JPM can detect single microwave photons with large bandwidth and with near unit efficiency (PRB 86, 174506 (2012)). The switching of a JPM into its voltage state acts on the adjacent cavity via the back action of photon subtraction (PRA 86, 032311 (2012)). While a destructive measurement of the microwave cavity, this switching can perform a binary non-demolition measurement of a quantum system coupled to the cavity. We present a protocol by which the presence and subsequent detection of a cavity photon by a JPM conveys information about the state of a superconducting qubit without destroying it, thus performing a quantum non-demolition measurement of the qubit's state. Multi-qubit generalizations of this protocol are discussed.