Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Frontiers in Optics

Engineering a Noiseless and Broadband Raman Quantum Memory for Temporal Mode Manipulation

T. M. Hird, Sarah E. Thomas, J. H. D. Munns, O. Lazo-Arjona, Shaobo Gao, J. Nunn, Benjamin Brecht, D. J. Saunders, Patrick M. Ledingham, Ian A. Walmsley

Published Jan 1, 2018• 1 citation
Publisher

Abstract

The Raman quantum memory can manipulate temporal modes of light -a promising high-dimensional basis for quantum information processing. We demonstrate both temporal mode manipulation and a novel suppression scheme for four-wave mixing noise.
DOI
10.1364/fio.2018.jw3a.63

Related papers

Engineering a noise-free quantum memory for temporal mode manipulation

T. M. Hird

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. 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. 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. 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.

•Jan 1, 2021•0 citations

Efficient, low noise, mode-selective quantum memory

Sarah E. Thomas

Photonic quantum information processing is a key element for scalable quantum technologies, and has applications in secure long-distance quantum communication and connecting nodes of a quantum computation network. However, logical photon-photon gates and state-of-the-art single photon sources rely on probabilistic processes. Quantum memories are devices that enable storage and on-demand recall of quantum states of light, and have been highlighted as a vital component in photonic networks to overcome the scaling problem by synchronising probabilistic processes. The Raman memory has a large storage bandwidth and high synchronising capacity, and is an ideal candidate for local synchronisation. However, previous demonstrations of the Raman memory suffer from four-wave mixing noise, which prohibits quantum level operation. In this thesis I investigate methods to increase the signal to noise ratio in the Raman memory. I investigate increasing the light-matter coupling strength to boost the memory efficiency, and then explore two different methods to suppress four-wave mixing noise. I demonstrate that operating the Raman memory in a cavity is successful in reducing four-wave mixing, but it is technically challenging to maintain a high memory efficiency. I investigate a new method of noise suppression by introducing an absorption feature at the frequency of the unwanted noise field. This technically simple method is successful in reducing the noise by an order of magnitude, and will be applicable to many quantum memory protocols. In the final section of this thesis I explore the temporal mode properties of the Raman memory. I demonstrate that the Raman memory is single mode and can be used to separate and manipulate temporal modes of light. This positions the Raman memory as a key device for enabling high-dimensional photonic quantum information processing, and enhancing light-matter interactions. These results pave the way towards an efficient, low-noise, mode-selective quantum memory.

•Apr 1, 2019•0 citations

A Cavity-Enhanced Room-Temperature Broadband Raman Memory

Patrick M. Ledingham, J. H. D. Munns, Sarah E. Thomas +8 more

Quantum memories enable the synchronisation of photonic operations. Raman memories are a promising platform, but are susceptible to four-wave mixing noise. We present a demonstration of a cavity-enhanced Raman memory, showing suppression of four-wave mixing.

Conference on Lasers and Electro-Optics•Jan 1, 2016•1 citation

Raman quantum memory with built-in suppression of four-wave-mixing noise

Sarah E. Thomas, T. M. Hird, J. H. D. Munns +5 more

Quantum memories are essential for large-scale quantum information networks. Along with high efficiency, storage lifetime, and optical bandwidth, it is critical that the memory adds negligible noise to the recalled signal. A common source of noise in optical quantum memories is spontaneous four-wave mixing. We develop and implement a technically simple scheme to suppress this noise mechanism by means of quantum interference. Using this scheme with a Raman memory in warm atomic vapor, we demonstrate over an order of magnitude improvement in noise performance. Furthermore we demonstrate a method to quantify the remaining noise contributions and present a route to enable further noise suppression. Our scheme opens the way to quantum demonstrations using a broadband memory, significantly advancing the search for scalable quantum photonic networks.

arXiv:1905.00042•Physical Review A•Sep 3, 2019•38 citations

Bad Cavities for Good Memories: Suppression of Four-Wave Mixing in Raman Memories

J. H. D. Munns, Tessa F. M. Champion, Cheng Qiu +4 more

Quantum memories enable the synchronisation of photonic operations. Raman memories are a promising platform, but are susceptible to four-wave mixing noise. We present a demonstration of a cavity-enhanced Raman memory, showing suppression of four-wave mixing.

Frontiers in Optics•Jan 1, 2015•0 citations

Optimisation and applications of a Raman quantum memory for temporal modes of light

J. H. D. Munns

Within any practical proposal for utilising quantum mechanics for information processing whether for the efficient computation of problems intractable by classical methods, or for secure communication; at some stage one must have the means to transfer quantum information between remote nodes of a network. For this, light is the obvious choice. To realise this vision one requires the means to overcome the ``scaling problem'' intrinsic to many photonic-based quantum technologies due to probabilistic operations. It has been identified that optical quantum memories which facilitate the storage and retrieval of quantum states of light are an enabling technology. Another requisite technology to ensure the scalability of a quantum network is the means to interface dissimilar material nodes, which in practice means the translation of quantum light in bandwidth, frequency and temporal shape. The first part of this thesis presents experimental, theoretical and numerical investigations of noise reduction in the Raman memory protocol in thermal caesium vapour, by means of a cavity. To do this, I develop a theoretical description of the cavity memory interaction, along with a model of the atom-cavity system to enable meeting the required resonance conditions. This is followed by a proof-of-concept experimental demonstration, showing suppression of noise in the retrieved state. To conclude this part, I investigate the optimisation of this system and provide a numerical framework for its design, and propose a route towards realising the Raman memory as a practical quantum memory. The second theme is an exploration of the practical application of the Raman memory as an interface for temporal modes of light. I perform a preliminary investigation, and develop characterisation tools, to experimentally verify the modal structure of the memory interaction. This work provides the basis for deploying the Raman memory as a temporal-mode selective device for GHz bandwidth quantum states of light.

•May 1, 2018•0 citations
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. 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. 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. 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.
Photonic quantum information processing is a key element for scalable quantum technologies, and has applications in secure long-distance quantum communication and connecting nodes of a quantum computation network. However, logical photon-photon gates and state-of-the-art single photon sources rely on probabilistic processes. Quantum memories are devices that enable storage and on-demand recall of quantum states of light, and have been highlighted as a vital component in photonic networks to overcome the scaling problem by synchronising probabilistic processes. The Raman memory has a large storage bandwidth and high synchronising capacity, and is an ideal candidate for local synchronisation. However, previous demonstrations of the Raman memory suffer from four-wave mixing noise, which prohibits quantum level operation. In this thesis I investigate methods to increase the signal to noise ratio in the Raman memory. I investigate increasing the light-matter coupling strength to boost the memory efficiency, and then explore two different methods to suppress four-wave mixing noise. I demonstrate that operating the Raman memory in a cavity is successful in reducing four-wave mixing, but it is technically challenging to maintain a high memory efficiency. I investigate a new method of noise suppression by introducing an absorption feature at the frequency of the unwanted noise field. This technically simple method is successful in reducing the noise by an order of magnitude, and will be applicable to many quantum memory protocols. In the final section of this thesis I explore the temporal mode properties of the Raman memory. I demonstrate that the Raman memory is single mode and can be used to separate and manipulate temporal modes of light. This positions the Raman memory as a key device for enabling high-dimensional photonic quantum information processing, and enhancing light-matter interactions. These results pave the way towards an efficient, low-noise, mode-selective quantum memory.
Quantum memories are essential for large-scale quantum information networks. Along with high efficiency, storage lifetime, and optical bandwidth, it is critical that the memory adds negligible noise to the recalled signal. A common source of noise in optical quantum memories is spontaneous four-wave mixing. We develop and implement a technically simple scheme to suppress this noise mechanism by means of quantum interference. Using this scheme with a Raman memory in warm atomic vapor, we demonstrate over an order of magnitude improvement in noise performance. Furthermore we demonstrate a method to quantify the remaining noise contributions and present a route to enable further noise suppression. Our scheme opens the way to quantum demonstrations using a broadband memory, significantly advancing the search for scalable quantum photonic networks.
Within any practical proposal for utilising quantum mechanics for information processing whether for the efficient computation of problems intractable by classical methods, or for secure communication; at some stage one must have the means to transfer quantum information between remote nodes of a network. For this, light is the obvious choice. To realise this vision one requires the means to overcome the ``scaling problem'' intrinsic to many photonic-based quantum technologies due to probabilistic operations. It has been identified that optical quantum memories which facilitate the storage and retrieval of quantum states of light are an enabling technology. Another requisite technology to ensure the scalability of a quantum network is the means to interface dissimilar material nodes, which in practice means the translation of quantum light in bandwidth, frequency and temporal shape. The first part of this thesis presents experimental, theoretical and numerical investigations of noise reduction in the Raman memory protocol in thermal caesium vapour, by means of a cavity. To do this, I develop a theoretical description of the cavity memory interaction, along with a model of the atom-cavity system to enable meeting the required resonance conditions. This is followed by a proof-of-concept experimental demonstration, showing suppression of noise in the retrieved state. To conclude this part, I investigate the optimisation of this system and provide a numerical framework for its design, and propose a route towards realising the Raman memory as a practical quantum memory. The second theme is an exploration of the practical application of the Raman memory as an interface for temporal modes of light. I perform a preliminary investigation, and develop characterisation tools, to experimentally verify the modal structure of the memory interaction. This work provides the basis for deploying the Raman memory as a temporal-mode selective device for GHz bandwidth quantum states of light.