Speaker
Description
Vacuum fluctuations play a decisive role in many effects in quantum field theory and cosmology. When a parameter in the Lagrangian of the field is modulated by an external pump, vacuum fluctuations stimulate spontaneous downconversion processes, resulting in squeezing between modes symmetric with respect to half of the frequency of the pump. We have observed this phenomenon in the microwave domain, by using an array of SQUIDs with flux-bias tunable Josephson inductance, which creates a tunable speed of light along the array. We have extracted the full 4 × 4 covariance matrix of the emitted microwave radiation, demonstrating that photons at frequencies symmetrical with respect to half of the modulation frequency are entangled [PNAS 110, 4234 (2013)]. Next, we have shown that by double parametric pumping of a superconducting microwave cavity, it is possible to generate another type of correlation, namely coherence between photons in separate frequency modes [Nature Communications 7, 12548 (2016)]. The coherence correlations are controllable by the phases of the pumps and are established by a quantum fluctuation that stimulates the simultaneous creation of two photon pairs. We have shown that the origin of this vacuum-induced coherence is the absence of which-way information in the frequency space. In this contribution I will also discuss the prospects of utilizing superconducting circuits for realizing analog relativistic and cosmological effects.
| Topic: | Mini-workshop: Continuous Variables and Relativistic Quantum Information |
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