LSP:Quantum Optics

Quantum Optics - Theory

Current research topics

Creation of single time-bin entangled photon pairs from single emitters

For applications in quantum information processing and quantum communication it is desirable to have sources of entangled photons that can be guaranteed to produce at most a single pair, unlike parametric down-conversion, which is currently the standard source of entangled photons. We have recently proposed a general way for realizing such a single-pair source based on single emitters. Unlike previous proposals, which focused on polarization entanglement, we suggest to create time-bin entangled photons, which are particularly well suited for long-distance quantum communication. From an experimental point of view, we are particularly interested in the possibility of realizing the proposal with quantum dots.

Reference:

C. Simon and J.-P. Poizat, Creating single time-bin entangled photon pairs, quant-ph/0409100

Multiphoton entanglement

We explore the possibility of creating strongly entangled states of large numbers of photons via parametric down-conversion. The work is done in collaboration with the group of Prof. Dirk Bouwmeester at the University of California Santa Barbara. On the theoretical side, we have begun to develop the theory of an “entanglement laser” based on down-conversion in a cavity. Another important part of the theoretical work is the development of criteria for the detection of the multiphoton entanglement. Finally we are thinking about possible applications of the generated multiphoton entanglement, for example for quantum key distribution.

References:

H.S. Eisenberg, G. Khoury, G. Durkin, C. Simon, and D. Bouwmeester, Quantum entanglement of a large number of photons, quant-ph/0408030, to appear in Phys. Rev. Lett.

G. Durkin, C. Simon, J. Eisert, and D. Bouwmeester, Resilience of multiphoton entanglement under losses, quant-ph/0402053, to appear in Phys. Rev. A

C. Simon and D. Bouwmeester, Theory of an Entanglement Laser, Phys. Rev. Lett. 91, 053601 (2003).

G. Durkin, C. Simon, and D. Bouwmeester, Multiphoton Entanglement Concentration and Quantum Cryptography, Phys. Rev. Lett. 88, 187902 (2002)

Towards quantum superpositions of a mirror.

This ambitious project, which is done in collaboration with the Bouwmeester group at UCSB, aims to create and detect quantum superpositions states of a small mirror. At the moment the theoretical work focuses on methods for detecting and possibly cooling the motion of the mirror optically, taking into account the limitations imposed by the heating of the mirror through absorption of the laser light.

References:

W. Marshall, C. Simon, R. Penrose, and D. Bouwmeester, Towards quantum superpositions of a mirror, Phys. Rev. Lett. 91, 130401 (2003).

C. Seife, "Quantum experiment asks "how big is big?", Science 298: 342-343 Oct 11, 2002

C. Choi, "Scaled-Up Superposition", Scientific American Feb 2003

Quantum computing with optically controlled individual spins in quantum dots

We study the possibility of realizing quantum computing in the solid state, using individual spins in quantum dots as the qubits. We are particularly interested in schemes where the dynamics is controlled optically with ultrafast laser pulses. The project is pursued in collaboration with colleagues in the Service for Physics of Materials and Microstructures of the CEA Grenoble.

Experimental tests of hidden-variable theorems

The goal of this area of work, which is done in collaboration with the Bouwmeester group at UCSB, is to make experimental tests of Bell’s theorem even more convincing by designing experiments that close the remaining “loopholes” or that exhibit the contradiction between the predictions of local hidden variables and physical reality in a particularly striking way.

References:

W.T.M. Irvine, J.F. Hodelin, C. Simon, and D. Bouwmeester, Realisation of Hardy’s Thought Experiment, quant-ph/0410160, submitted to Phys. Rev. Lett.

C. Simon and W.T.M. Irvine, Robust long-distance entanglement and a loophole-free Bell test with ions and photons, Phys. Rev. Lett. 91, 110405 (2003).