Quantum Tomography of Photon States Encoded in Polarization and Time

  Pini Zilber  ,  Yehuda Pilnyak  ,  Hagai Eisenberg  
Racah Institute of Physics, The Hebrew University of Jerusalem, Israel

We introduce a two-qubit information system, realized by two degrees of freedom in a single photon: polarization and time. The photon arrival time is divided into two time-bins, and any superposition of them is possible. In our work, the difference between the time-bins of the photons we produced is less than a picosecond – much less than the detectors time resolution.

We demonstrate the reconstruction of two-qubit information encoded in a photon using quantum state tomography. The projection on different states was measured by the amount of bunching on a beam splitter with an ancilla photon of the projected state. We reconstruct superpositions of two time-bins with sensitivity to the phase difference between them. Different quantum states were reconstructed, with fidelities higher than 96%.