Broadband Quantum Memories

We are developing a quantum memory for the storage of ultra-short photons in an atomic media.

Quantum photonics seeks to harness the peculiar properties of quantum mechanics - in particular superpositions and entanglement - to create novel technologies such as quantum computers. Due to their negligible interactions, photons are ideal for the transmission of quantum information. Furthermore recent advances in photon technologies have facilitated the production of exotic multi-photon, multi-mode quantum states of light.

However, the very properties that make light the ideal medium for transporting quantum information, makes it hard to store the information, hence a critical element of complex quantum-photonic systems is a quantum memory. A quantum memory is an interface between light and matter that allows for the storage and retrieval of photonic quantum information, analogous to the memory in a normal computer. However, the power of quantum computation relies on maintaining a non-classical superposition of quantum states, as soon as the state is measured, the superposition is destroyed and the information becomes classical. Therefore, it it is crucial to the success of a quantum memory, that it faithfully reproduces the state in such a way that a measurement can never be made of the system while it is stored. Herein lies the challenge of producing a quantum memory.

With data rates escalating across the world, we are continually searching for faster ways to transmit data. Therefore, we would ultimately like quantum information to be transmitted in ultra-short laser pulses. This places further requirements on prospective quantum memories as they must be capable of supporting the large bandwidths involved. Our work focusses on sub-nanosecond pulses with the potential of storing, and retrieving, data at gigahertz bandwidths at the single-photon level.

The concept of an off-resonant atomic quantum memory based on a Raman interaction was first suggested by this group in 2007. In 2009, the Raman memory was demonstrated using room-temperature Caesium vapour to store pulses of 300ps (0.3 billionths of a second) duration. Click here to read the original paper. Current research revolves around developing this technology to store exotic states of quantum light.