**Special Winter Seminar Series - Quantum Computing and Information**

**Measuring the number of photons in a microwave mode**

Benjamin Huard – ENS Lyon

Counting the number of photons in an electromagnetic mode is an important tool for quantum information processing. In order to perform a single shot measurement, one usually encodes information about the photon number into a qubit state and read out the qubit. Repeating this procedure while varying the encoded single bit of information allows us to pinpoint the number of photons. In this talk, I will present two experiments that address two main challenges in photocounting.

First, I will show how one can avoid the sequential repetition of qubit measurements and instead use a single superconducting qubit in order to multiplex the measurement of the photon number in a stationary microwave mode.

Second, I will show how we could convert a stationary mode counter into a photocounter of traveling wave packets using a quantum memory.

*All interested persons are invited to attend remotely—email physics@nd.edu for information.*