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Quantum interference between two single photons of different microwave frequencies



Francois E. Nguyen, Eva A. Zakka-Bajjani, Jose A. Aumentado, Raymond W. Simmonds


Quantum interference is an important tool for fields such as lithography, metrology and quantum processing. Two identical optical photons (photons with the same wavelength and polarization) simultaneously sent through the two input ports of a semi-transparent (50:50) beam-splitter (BS) will exit together in the same output port. This is a consequence of a complete destructive quantum interference between the two indistinguishable paths in which the photons would exit by two different outputs. This effect was first experimentally observed in parametric down-conversion, and more recently by use of various, distinct or not, single-photon sources. It is at the heart of the recent dual-rail linear optical quantum computing schemes, where information is encoded on different spatial modes. Here, we show such a quantum interference effect between two single microwave photons trapped in a superconducting resonator, whose frequencies are initially distinguishable (6 GHz apart). We accomplish this by use of a parametric frequency conversion (PFC) process that mixes the mode currents of two cavity harmonics through a superconducting interference device (SQUID).


Nguyen, F. , Zakka-Bajjani, E. , Aumentado, J. and Simmonds, R. (2012), Quantum interference between two single photons of different microwave frequencies, Nature, [online], (Accessed April 21, 2024)
Created April 20, 2012, Updated November 10, 2018