| Summary: | <p>An optical quantum memory, a device which can store and retrieve on demand an arbitrary
quantum state at the single photon level, has been identified as a significant cornerstone
of photonic quantum technologies. The development of such a memory would allow the
creation and development of a large number of quantum technologies. These would range
from the ability to synchronise processing steps in an optical quantum computer, to the
construction of a quantum repeater which would allow faithful transmission of quantum
states over arbitrarily long distances.
</p>
<p>In this thesis I investigate broadband light storage in a room-temperature Raman memory
for purposes of quantum information processing with photons. During the course of this
thesis, a novel scheme to suppress four-wave mixing noise is simulated, based on equations
derived to describe the physics of the memory interaction. The experimental arrangement
to test the suppression method is described and an original method using photon statistics is
demonstrated. The results of these experiments prove the ability of the memory to retrieve
and maintain the non-classicality of the state, given a single photon input.</p>
<p>Following the affirmation that, using this noise suppression technique, the memory can
function at the single-photon level, I go on to consider how the temporal-spectral properties
of a pulsed mode of light may be manipulated using the memory. There are two primary
reasons for this investigation: 1) Increasing the efficiency of the read-in process by carving
the optimum mode of the memory 2) Using the memory as a device operating in a high dimensional
quantum information basis. The restrictions of such applications are considered
and a method to test the efficacy of transformations in this basis is devised and experimentally
tested. I also perform demonstrations of light storage using conventional temporal
modes using a novel method of velocity selection within warm vapour.</p>
<p>Finally I detail further experiments that are achievable with the Raman quantum memory
given the progress that has been achieved during my DPhil research. The results show that
the Raman memory is a viable candidate for a practical route towards low-noise quantum
storage and for manipulation of temporal modes of light.</p>
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