Speaker
Prof.
Robert McDermott
(UW-Madison)
Description
The Josephson photomultiplier (JPM) is the microwave-frequency analog of the avalanche photodiode: absorption a single photon induces a transition between distinct macroscopic states, resulting in an easily measured “click”. In the most common implementation, the junction plasma resonance is tuned to the desired detection frequency, and photon absorption enables a tunneling transition between distinct circulating current states in an rf SQUID loop. We have used the JPM to perform fast, high-fidelity quantum nondemolition measurement of a superconducting qubit. Here we map the qubit state to bright and dark microwave pointer states in a linear cavity. The JPM detects the presence or absence of photons, projecting the qubit into the appropriate computational basis state. Crucially, the approach provides access to the classical bit that is the result of projective quantum measurement at the millikelvin stage, without the need for quantum limited amplification of the measurement tone or heterodyning and thresholding at room temperature.
Primary author
Prof.
Robert McDermott
(UW-Madison)
