Generation and tomography of arbitrary optical qubits using transient collective atomic excitations University of Calgary | Publication | 2014-01-01 | T. Brannan, Z. Qin, A. MacRae, A. Lvovsky |

Generation and tomography of arbitrary qubit states using transient collective atomic excitations University of Calgary | Publication | 2014-01-01 | T. Brannan, Z. Qin, A. MacRae, A. Lvovsky |

Towards engineering arbitrary superpositions of collective spin excitations University of Calgary, University of Alberta | Presentation | 2012-07-23 | T. Brannan, A. MacRae, R. Achal, A. Lvovsky |

Tomography of a high-purity narrowband photon from four-wave mixing in atomic vapourMuch work has been done in recent years to develop interesting quantum states in the optical regime. A natural step forward would be to extend our quantum state engineering abilities to collective spin excitations (CSE’s) in hot atomic vapour. Such an extension could find applications in quantum memory, long distance quantum communication, quantum logic gates, and quantum metrology. We demonstrate a setup that serves as a high quality single photon source and a first step towards quantum state engineering of arbitrary states in CSE’s.
We use four-wave mixing in a hot atomic vapour cell to create a two-mode squeezed state, similar to parametric down conversion. Heralding on a single photon event in one channel yields a high purity narrow-bandwidth single photon in the other channel. Employing optical homodyne tomography, we reconstruct the density matrix of the generated photon and observe a Wigner function reaching the zero value without correcting for inefficiencies. The intrinsic narrow bandwidth and high production rate of our system result in a high spectral brightness source. Since these photons are also naturally resonant to atomic transitions, our source is attractive for applications in light-atom interfacing.
Moving to the pulsed regime would allow for time separated events of CSE creation and optical readout, akin to the well-known DLCZ scheme. Conditional measurements during the write phase prepare the CSE in an arbitrary superposition state, which can then be read out optically and measured via homodyne tomography.
University of Calgary, University of Alberta | Presentation | 2012-08-16 | T. Brannan, A. MacRae, R. Achal, A. Lvovsky |

Measuring the temporal wavefnction of a photonHomodyne tomography provides information about the signal state of the electromagnetic field in the mode of the local oscillator. If the signal state is known to be the signal photon, the mode of that photon can be determined by searching for the temporal shape of the local oscillator pulse such that the observed single-photon efficiency is maximized. However, if the bandwidth of the temporal mode of the photon is sufficiently narrow in comparison with those of the detector and the acquisition system, the same task can be solved with a continuous local oscillator, thereby greatly simplifying the experimental procedure. Complete information about the mode can be obtained from the autocorrelation statistics of the homodyne photocurrent acquired at several different local oscillator frequencies. We present a theory and experiment to demonstrate the capabilities of this technique. A heralded single photon is obtained from a pair generated via four-wave mixing in an atomic vapor and the required bandwidth is achieved by spectral filtering of the trigger channel by means of a narrowband optical cavity. University of Calgary | Presentation | 2013-07-18 | T. Brannan, Z. Qin, A. MacRae, A. Lezama, A. Lvovsky |

Tomography of a High-Purity Narrowband Photon from a Transient Atomic Collective Excitation University of Calgary, University of Alberta | Publication | 2012-07-01 | A. MacRae, T. Brannan, R. Achal, A. Lvovsky |

Engineering of optical states from an atomic source University of Calgary | Presentation | 2011-11-10 | A. MacRae, T. Brannan, A. Lvovsky |

Towards quantum engineering University of Calgary | Presentation | 2012-01-04 | A. MacRae, T. Brannan, A. Lvovsky |

Tomography of single photons and qubits generated by atoms University of Calgary, University of Alberta | Presentation | 2012-07-04 | A. MacRae, T. Brannan, R. Achal, A. Lvovsky |

Single photons generated by atoms University of Calgary, University of Alberta | Presentation | 2012-05-23 | A. MacRae, T. Brannan, P. Palittapongarnpim, R. Achal, A. Lvovsky |

Generation of arbitrary quantum states from atomic ensembles University of Calgary, University of Alberta | Presentation | 2012-06-11 | A. MacRae, T. Brannan, R. Achal, A. Lvovsky |

Narrowband Photon from an Atomic SourceWe demonstrate efficient generation of narrow-bandwidth photon superposition states. Since the heralded states stem from a transient collective spin excitation in the atomic ensemble, this work allows the engineering of arbitrary collective atomic excitation states. University of Calgary | Presentation | 2012-10-17 | A. MacRae, T. Brannan, A. Lvovsky |

Generation of arbitrary quantum states from atomic ensembles University of Calgary, University of Alberta | Publication | 2012-09-01 | A. MacRae, T. Brannan, R. Achal |

Measuring the temporal wave function of a photon University of Calgary | Presentation | 2014-05-29 | Z. Qin, A. Prasad, T. Brannan, A. MacRae, A. Lezama, A. Lvovsky |

Complete temporal characterization of a single photon University of Calgary | Publication | 2014-05-01 | Z. Qin, A. Prasad, T. Brannan, A. MacRae, A. Lezama |