Thread by @fgrosshans

Now, Nobuyuki Imoto from @osaka_univ_e on Frequency conversion of single photons emitted from atom/ion quantum memory for telecommunications #LTQI

@osaka_univ_e Noboyuki Imoto’s focus is on a global quantum network. It is useful for long haul QKD, the goal is to go beyond the *relayed* quantum network of journals.aps.org/prl/abstract/1… #LTQI

@osaka_univ_e Nobuyuki Imoto works on quantum repeaters in a fibre network. He limits the decoherence via decoherence free subspaces (DFS). #LTQI

@osaka_univ_e Nobuyuki Imoto: Error correcting codes need at least 5 qubits, which makes them useless in this case. DFS allows to to use 2 physical qubits/qubit, and encode the wuibit in their relative phase. #LTQI

@osaka_univ_e Nobuyuki Imoto: It is easy when one prepares the qubit. But to encode an unknown qubit which is given to you? #LTQI

@osaka_univ_e Nobuyuki Imoto: The problem: using 2 photons implies a scaling in T². Can we reduce the scaling to T¹ ? Surprisingly, yes! #LTQI

@osaka_univ_e Nobuyuki Imoto: up to now, we only spoke about phase noise. A more recent work is on suppressing both phase and ploarization noise. #LTQI

@osaka_univ_e Nobuyuki Imoto also uses PPLN to frequency convert single photons, keeping the entanglement. #LTQI

@osaka_univ_e Nobuyuki Imoto Putting tha quantum frequency (QFC) converter (the PPLN crystal) in a Sagnac interferometer allows to build a polarization insensitive QFC. #LTQI