Heralded generation of programmable two-qubit entangled states on a linear-optical platform

N. N. Skryabin, Yu. A. Biriukov, M. A. Dryazgov, S. A. Fldzhyan, S. A. Zhuravitskii, A. S. Argenchiev, I. V. Kondratyev, L. A. Tsoma, K. I. Okhlopkov, I. M. Gruzinov, A. Ya. Arsenyev, K. V. Taratorin, M. Yu. Saygin, I. V. Dyakonov, M. V. Rakhlin, A. I. Galimov, G. V. Klimko, S. V. Sorokin, I. V. Sedova, M. M. Kulagina, Yu. M. Zadiranov, A. A. Toropov, S. A. Evlashin, A. A. Korneev, S. P. Kulik, S. S. Straupe

Source abstract

We present an experimental platform for linear-optical quantum information processing. Our setup utilizes multiphoton generation using a high-quality single-photon source, which is demultiplexed across multiple spatial channels, a custom-designed, programmable, low-loss photonic chip, and paired with high-efficiency single-photon detectors. We demonstrate the platform’s capability heralded generation of arbitrary two-qubit dual-rail encoded states, including Bell states. Bell states are an invaluable resource for boosting the fusion gates within a photonic quantum computer [ Phys. Rev. Lett. 115 , 020502 ( 2015 ) 10.1103/PhysRevLett.115.020502 ], The programmable chip was fully characterized through a calibration process that allowed us to create a numerical model that accounts for fabrication imperfections and measurement errors. As a result, using on-chip quantum state tomography (QST), we achieved high-fidelity quantum state preparation, with a fidelity of 98.5% specifically for the Bell state postselected in the dual-rail basis.