Complete characterization of quantum-optical processes.
Science (New York, N.Y.) 322:5901 (2008) 563-566
Abstract:
The technologies of quantum information and quantum control are rapidly improving, but full exploitation of their capabilities requires complete characterization and assessment of processes that occur within quantum devices. We present a method for characterizing, with arbitrarily high accuracy, any quantum optical process. Our protocol recovers complete knowledge of the process by studying, via homodyne tomography, its effect on a set of coherent states, that is, classical fields produced by common laser sources. We demonstrate the capability of our protocol by evaluating and experimentally verifying the effect of a test process on squeezed vacuum.Photons as quasicharged particles
Physical Review A American Physical Society (APS) 77:4 (2008) 043813
Quantum memory for squeezed light.
Physical review letters 100:9 (2008) 093602
Abstract:
We produce a 600-ns pulse of 1.86-dB squeezed vacuum at 795 nm in an optical parametric amplifier and store it in a rubidium vapor cell for 1 mus using electromagnetically induced transparency. The recovered pulse, analyzed using time-domain homodyne tomography, exhibits up to 0.21+/-0.04 dB of squeezing. We identify the factors leading to the degradation of squeezing and investigate the phase evolution of the atomic coherence during the storage interval.Adiabatic frequency conversion of optical information in atomic vapor.
Optics letters 32:19 (2007) 2771-2773
Abstract:
We experimentally demonstrate a communication protocol that enables frequency conversion and routing of quantum information in an adiabatic and thus robust way. The protocol is based on electromagnetically induced transparency (EIT) in systems with multiple excited levels: transfer and/or distribution of optical states between different signal modes is implemented by adiabatically changing the control fields. The proof-of-principle experiment is performed using the hyperfine levels of the rubidium D1 line.Time-resolved probing of the ground state coherence in rubidium.
Optics letters 32:12 (2007) 1755-1757