Christopher Wilson, 04/04/2011

Microwave Quantum Optics Using Superconducting Circuits

Christopher Wilson
Quantum Device and Physics Laboratory, Chalmers University, Sweden

We describe the results of two experiments. In the first, we report the observation of photon generation in a microwave cavity with a time-dependent boundary condition.  Our system is a microfabricated quarter-wave coplanar waveguide cavity. The electrical length of the cavity is varied using the tunable inductance of a SQUID.  When the length is modulated at approximately twice the static resonance frequency, spontaneous parametric oscillations of the cavity field are observed.  Time-resolved measurements of the dynamical state of the cavity show multiple stable states. The behavior is well described by theory.  Our results may be considered a preliminary step towards the demonstration of the dynamical Casimir effect.  In the second experiment, we have embedded an artificial atom, a superconducting "transmon" qubit in a 1D open space and investigated the scattering of incident microwave photons. When an input coherent state, with an average photon number much less than 1, is on resonance with the artificial atom, we observe extinction of up to 90% in the forward propagating field.  By applying a second control tone, we have observed electromagnetically induced transparency (EIT). We use EIT to make a single photon router, where we can control to what output port an incoming signal is delivered.  The maximum on-off ratio is around 90% with a rise and fall time on the order of nanoseconds.

Fecha: Lunes 4 de Abril, 2011
Hora: 16:00
Lugar: Sala de Seminarios CFMAC, Serrano 121, Madrid