Download Quantum Memories at Room-Temperature Supervisors: Dr Dylan

Quantum Memories at Room-Temperature
Supervisors: Dr Dylan Saunders (Primary) and Prof. Ian Walmsley
Local Supervisor: Prof. Myungshik Kim (Imperial)
Background: Photonics is an exciting platform for exploring quantum phenomena at roomtemperature. However, photon loss and the probabilistic operation of quantum operations prohibit
the scaling of experiments to a regime where large numbers of photons can be prepared in
quantum-correlated states.
Here at the Ultrafast Quantum Optics Group (UFQO) at the
University of Oxford we have been exploring the use of twophoton interactions in warm Alkali vapours as a potential
solution to this scaling problem. The solution we are
proposing is to synchronise the output of multiple nondeterministic photonic operations using quantum memories
[1]. Briefly, a quantum memory is a device that maps flying
photons onto atoms, encoding the state of the light field
into a “hologram” formed by superpositions of excited
atoms across an ensemble of warm atoms at room
temperature in a robust simple package. The photons can
be recalled on demand after a programmable delay: a
light-matter beam-splitter.
The energy level diagrams of the
two memory protocols. Showing
the strong control field (bold), the
signal field (s), anti-stokes (a) and
stored coherence (b).
For the Master’s project, we are proposing an investigation into a new noise-suppression technique
in our lambda Raman quantum memory. This will be demonstration of a new protocol: a quantum
Zeno noise suppression technique to kill a noise-process prohibits quantum operation, a process
known as four-wave-mixing. We will suppress two-mode-squeezing via incoherent Hamiltonian
engineering. This work, and the PhD work, would be undertaken at the University of Oxford, in the
quantum memories sub-team within the UFQO.
For the PhD Project, you would continue to develop the quantum Zeno noise suppression
technique, incorporating it into our recently demonstrated Cavity enhanced quantum memory [2]
and interface with a novel new photon source [3]. Moving onto a demonstration of coherent
Hamiltonian engineering to suppress noise we will use the Zeno effect to select either the beamsplitter or two-mode squeezing interactions as shown in the figure. As the project matures we will
interface our new memory in a compact miniaturised form in the following experiments: lightmatter Hong-Ou-Mandel interference: to certify the quality of the memory operation; and the
manipulation of time-frequency modes [4], a completely new concept for compact information
storage in a light beam.
References:
[1] J. Nunn et. al. Enhancing Multiphoton Rates with Quantum Memories PRL 110, 133601 (2013)
[2] D. Saunders et. al. Cavity-Enhanced Room-Temperature Broadband Raman Memory PRL 116,
090501 (2016)
[3]. B. Brecht et al. A versatile design for resonant guided-wave parametric down-conversion sources
for quantum repeaters, Appl. Phys. B 122: 116 (2016)
[4] B. Brecht et al. Photon Temporal Modes: A Complete Framework for Quantum Information
Science PRX, 5, 041017 (2015).