# Quantum Reservoir Engineering in Circuit QED

September 14, 2015 - 11:00am
Speaker:
Steven M. Girvin
Institution:
Yale

Quantum systems are never completely isolated, but instead interact with degrees of freedom in the surrounding environment, eventually leading to decoherence of the system. The conventional route to long-lived quantum coherence involves minimizing coupling to the dissipative bath.  Paradoxically, it is possible in principle to instead engineer specific couplings to a quantum environment that allow dissipation to actually create and preserve coherence.  I present a simple scheme to engineer the photon shot noise in a microwave cavity so that it relaxes a qubit towards any desired point on the Bloch sphere [1] and which can autonomously stabilize the entanglement of a pair of qubits [2].  More recently we have realized a multi-qubit cooling scheme which preserves the total number of excitation quanta thus paving the way for quantum simulations of the Bose-Hubbard model within the canonical ensemble [3].

##### [1] ‘Cavity-Assisted Quantum Bath Engineering,’ K. W. Murch, U. Vool, D. Zhou, S. J. Weber, S. M. Girvin, and I. Siddiqi, Phys. Rev. Lett. 109, 183602 (2012).

[2] ‘Stabilizing entanglement autonomously between two superconducting qubits,’ S. Shankar, M. Hatridge, Z. Leghtas, K. M. Sliwa, A. Narla, U. Vool, S. M. Girvin, L. Frunzio, M. Mirrahimi, M. H. Devoret, Nature504, 419-422 (2013).
[3] ‘Cooling and Autonomous Feedback in a Bose-Hubbard chain,’ Shay Hacohen-Gourgy, Vinay Ramasesh, Claudia De Grandi, Irfan Siddiqi, S. M. Girvin, arXiv:1506.05837.

2400 Computer and Space Sciences
College Park, MD 20742