COHERENCE:
Cooperativity in Highly Excited Rydberg
Ensembles — Control and Entanglement
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SA VI — Rydberg photonics and laser technology

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Performance of saturated absorber Er-fibre oscillatorsOctober 2012
TOPTICA, Germany, in collaboration with Durham, UK

Stable femtosecond lasers have greatly simplied optical precision measurements. Current erbium fibre lasers at Toptica are based on saturated absorbers. The advantage of this technology over Kerr model locked lasers is that they can be built to be polarisation maintaining and reliably self starting. We characterise two femtosecond fibre lasers with respect to noise, spectral and temporal properties which are essential for applications in frequency referencing, pump-probe experiments and timing distribution. A balanced optical cross-correlation (BOC) setup is used to optimise radio frequency electronics for tight locking of two lasers and to characterise the intrinsic timing jitter, found to be 22 fs, integrated between 8 Hz and 39.3 MHz.


Quantum state control of stored Rydberg polaritonsOctober 2012
Durham, UK

Using a weak signal and strong control light fields, we have achieved storage of single photons as Rydberg polaritons. Using a microwave field to drive oscillations of the stored polaritons between neighbouring Rydberg states, we can induce and control long-ranged dipole-dipole interactions between the stored photons. For weak microwave powers, the range of the interactions is increased beyond the separation between the polaritons which leads to dephasing observed as a suppression of the retrieved photon number. The controllable interactions between the polaritons could be exploited to perform quantum operations on photonic qubits, e.g. to implement a controlled phase gate.

Above left: The retrieved photon signal shows a signature of non-classicality imposed by the Rydberg blockade mechanism, namely the suppression of photon coincidences at zero time delay (red bar). Above right: collective oscillations of the retrieved photon number.

Reference:
D. Maxwell, D. J. Szwer, D. Paredes-Barato, H. Busche, J. D. Pritchard, A. Gauguet, K. J. Weatherill, M. P. A. Jones, and C. S. Adams, Storage and Control of Optical Photons Using Rydberg Polaritons, Phys. Rev. Lett. 110, 103001 (2013), or see our full list of publications
Four wave mixing in a thermal gas involving Rydberg statesJune 2012
Stuttgart, Germany

Four-wave mixing is a spectroscopy technique to control the light emission of atoms in a coherent way. The combination of four-wave mixing with the strong interaction of Rydberg atoms allows for the generation of single photons, as it has been shown with a sample of ultracold atoms (Kuzmich et.al., Science 336, 887, 2012). Our plan is to convert this result to a thermal gas of atoms to build a room temperature single photon source. The observation of a four-wave mixing signal is a major milestone towards this goal.

Reference:
A. Koelle, G. Epple, H. Kuebler, R. Löw, and T. Pfau, Four-wave mixing involving Rydberg states in a thermal vapor cell, Phys. Rev A 85, 063821 (2012), or see our full list of publications
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