Search SciRate
5 results for au:Wenniger_I in:quant-ph
Show all abstracts
N. Coste, D. A. Fioretto, S. E. Thomas, S. C. Wein, H. Ollivier, I. Maillette de Buy Wenniger, A. Henry, N. Belabas, A. Harouri, A. Lemaitre, I. Sagnes, N. Somaschi, O. Krebs, L. Lanco, P. Senellart The frequency or color of photons is an attractive degree of freedom to encode and distribute the quantum information over long distances. However, the generation of frequency-encoded photonic qubits has so far relied on probabilistic non-linear single-photon sources and inefficient gates. Here, we demonstrate the deterministic generation of photonic qubits hyper-encoded in frequency and polarization based on a semiconductor quantum dot in a cavity. We exploit the double dipole structure of a neutral exciton and demonstrate the generation of any quantum superposition in amplitude and phase, controlled by the polarization of the pump laser pulse. The source generates frequency-polarization single-photon qubits at a rate of 4 MHz corresponding to a generation probability at the first lens of 28 $\pm$ 2%, with a photon number purity > 98%. The photons show an indistinguishability > 91% for each dipole and 88% for a balanced quantum superposition of both. The density matrix of the hyper-encoded photonic state is measured by time-resolved polarization tomography, evidencing a fidelity to the target state of 94 $\pm$ 8% and concurrence of 77 $\pm$ 2%, here limited by frequency overlap in our device. Our approach brings the advantages of quantum dot sources to the field of quantum information processing based on frequency encoding.
I. Maillette de Buy Wenniger, S. C. Wein, D. Fioretto, S. E. Thomas, C. Antón-Solanas, A. Lemaître, I. Sagnes, A. Harouri, N. Belabas, N. Somaschi, P. Hilaire, J. Senellart, P. Senellart Quantum emitters such as quantum dots, defects in diamond or in silicon have emerged as efficient single photon sources that are progressively exploited in quantum technologies. In 2019, it was shown that the emitted single photon states often include coherence with the vacuum component. Here we investigate how such photon-number coherence alters quantum interference experiments that are routinely implemented both for characterising or exploiting the generated photons. We show that it strongly modifies intensity correlation measurements in a Hong-Ou-Mandel experiment and leads to errors in indistinguishability estimations. It also results in additional entanglement when performing partial measurements. We illustrate the impact on quantum protocols by evidencing modifications in heralding efficiency and fidelity of two-qubit gates.
I. Maillette de Buy Wenniger, S. E. Thomas, M. Maffei, S. C. Wein, M. Pont, N. Belabas, S. Prasad, A. Harouri, A. Lemaître, I. Sagnes, N. Somaschi, A. Auffèves, P. Senellart Energy transfer between quantum systems can either be achieved through an effective unitary interaction or through the generation of entanglement. This observation defines two types of energy exchange: unitary and correlation energy. Here we propose and implement experimental protocols to access these energy transfers in interactions between a quantum emitter and light fields. Upon spontaneous emission, we measure the unitary energy transfer from the emitter to the optical field and show that it never exceeds half of the total energy and is reduced when introducing decoherence. We then study the interference of the emitted field and a laser field at a beam splitter and show that the energy transfers quantitatively depend on the quantum purity of the emitted field.
H. Ollivier, S. E. Thomas, S. C. Wein, I. Maillette de Buy Wenniger, N. Coste, J. C. Loredo, N. Somaschi, A. Harouri, A. Lemaitre, I. Sagnes, L. Lanco, C. Simon, C. Anton, O. Krebs, P. Senellart Hong-Ou-Mandel interference is a cornerstone of optical quantum technologies. We explore both theoretically and experimentally how the nature of unwanted multi-photon components of single photon sources affect the interference visibility. We apply our approach to quantum dot single photon sources in order to access the mean wavepacket overlap of the single-photon component - an important metric to understand the limitations of current sources. We find that the impact of multi-photon events has thus far been underestimated, and that the effect of pure dephasing is even milder than previously expected.
Hélène Ollivier, Ilse Maillette de Buy Wenniger, Sarah Thomas, Stephen Wein, Guillaume Coppola, Abdelmounaim Harouri, Paul Hilaire, Clément Millet, Aristide Lemaître, Isabelle Sagnes, Olivier Krebs, Loïc Lanco, Juan Carlos Loredo, Carlos Antón, Niccolo Somaschi, Pascale Senellart Single-photon sources based on semiconductor quantum dots have emerged as an excellent platform for high efficiency quantum light generation. However, scalability remains a challenge since quantum dots generally present inhomogeneous characteristics. Here we benchmark the performance of fifteen deterministically fabricated single-photon sources. They display an average indistinguishability of 90.6 +/- 2.8 % with a single-photon purity of 95.4 +/- 1.5 % and high homogeneity in operation wavelength and temporal profile. Each source also has state-of-the-art brightness with an average first lens brightness value of 13.6 +/- 4.4 %. Whilst the highest brightness is obtained with a charged quantum dot, the highest quantum purity is obtained with neutral ones. We also introduce various techniques to identify the nature of the emitting state. Our study sets the groundwork for large-scale fabrication of identical sources by identifying the remaining challenges and outlining solutions.