The Heisenberg uncertainty principle limits the ways in which it is possible to measure the state of things.  Historically, this has been seen as a bad thing. More recently, however, there has been an outbreak of proposals that suggest Heisenberg uncertainty could be used as an integral part of “quantum information systems”.  Of these, quantum key distribution (QKD) is the most advanced.  This technique allows the sharing of a secret key between remote parties over an open communication channel. Although QKD has been demonstrated in optical fibres over distances over 200km [1], beyond this distance it becomes very slow or even impossible to share a key.

One possible method to fix this problem is to build a quantum repeater [2]. These devices, which are yet to be demonstrated, will extend the range of quantum communication beyond the current limit.  Integral to proposed repeaters is some kind of memory capable of storing, and recalling on demand, quantum states of light [3].

Our approach to building a quantum memory relies on reversible absorption in an ensemble of atoms.  This is a photon-echo technique known as a “gradient echo memory” (GEM). Our scheme has a lot of interesting properties, including the ability to change the ordering, frequency and shape of the stored light pulses. [4]

[1] Optics Letters, Vol. 37, Issue 6, pp. 1008-1010 (2012)
[2] Nature Photonics 1 (2007), no. 3, 165–171.
[3] Nature Photonics 3 (2009), no. 12, 706–714.

The project could be experimental or involve theoretical modelling. While not essential, for experiments, any knowledge of lasers, atoms, quantum mechanics and LabVIEW will help, for theory, some experience with numberical modelling would be good.