November 2011
Abstracts of the QSIT Lunch Seminar, November 3, 2011
From Coulomb to photon blockade (and back)
Sebastian Schmidt, Institute for Theoretical Physics, ETH Zurich
Photon blockade is a quantum optical effect in which the presence of a single photon in a nonlinear cavity prevents other photons to enter. It is the basic underlying mechanism for the realization of strongly correlated photonic systems, e.g., a possible superfluid-Mott insulator transition of polaritons in a coupled cavity array. So far, it has been observed via resonant laser excitation in various cavity QED systems, i.e., by demonstrating antibunching of the photons leaking out of the cavity.
In a recent theory-experiment collaboration, we have outlined an alternative scheme for the observation of photon blockade in circuit QED (A. J. Homan et. al., PRL 107, 053602 (2011). A transmission line cavity is driven not by coherent radiation, but by incoherent radiation of a colored noise source. By varying the spectral bandwidth of the noise the transmission of photons through the cavity displays several steps similar to what is known as the current staircase for electron transport through Coulomb blockaded quantum dots.
In this talk, we discuss recent results on this new route towards photon blockade physics and stress analogies and differences to electron transport through quantum dots. Its potential relevance for the realization of strongly correlated and exotic states of light will also be discussed.
Co-authors: A. Hoffmann, H. Tureci, A. Houck: Department of Electrical Engineering, Princeton University, USA and G. Blatter: Institute for Theoretical Physics, ETH Zurich
Observation of Resonant Photon Blockade at Microwave Frequencies using Correlation Function Measurements
Christian Lang, Quantum Device Lab, ETH Zurich
Creating a train of single photons and monitoring its propagation and interaction is challenging in most physical systems, as photons generally interact very weakly with other systems. However, when confining microwave frequency photons in a transmission line resonator, effective photon-photon interactions can be mediated by qubits embedded in the resonator. Here, we observe the phenomenon of photon blockade through second-order correlation function measurements. The experiments clearly demonstrate antibunching in a continuously pumped source of single microwave photons measured using microwave beam splitters, linear amplifiers, and quadrature amplitude detectors. We also investigate resonance fluorescence and Rayleigh scattering in Mollow-triplet-like spectra.
C. Lang et al., Phys. Rev. Lett. 106, 243601 (2011)