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

Science

Probing Quantum Memories

Published Apr 5, 2007• 0 citations
Publisher

Abstract

Can't quite place a name to the face, or associate a singer with a song? You know, or at least hope, that the information lies intact somewhere in your head, needing only the correct memory trick or stimulus to retrieve it. For quantum communications, where information is transmitted along quantum channels and stored in quantum memories, it is necessary that the stored information be robust and retrievable. However, quantum memories are known to decay because of decoherence, and physicists therefore have to develop their own set of tricks to probe and measure how reliable these memories are. Staudt et al. look at quantum information stored in an optical memory, where the information is encoded in the coherent transfer of the phase and amplitudes of light pulses onto a suitable solid-state medium. They use a photon-echo technique whereby a sequence of pulses initializes the memory cell, encodes the data onto it, and uses a read pulse to generate a stimulated echo pulse which replicates the stored information. The advantage of this scheme is that, though memories may be lost, if they are recalled they remain undistorted. — ISO

DOI
10.1126/science.316.5821.19b

Related papers

Quantum optical storage and processing using raman gradient echo memory

Mahdi Hosseini

The non-interacting and high-speed nature of light makes it an ideal carrier of information that is essential for transmission of quantum information. Indeed, many proposals and demonstrations of quantum cryptography rely on the use of fibre-optic networks. Construction of a memory that can store light and preserve its quantum properties will be useful in a range of quantum information systems such as secure quantum communication and quantum computation. This is why a quantum memory for light is a remarkable objective. The key to quantum memory is to store the probability amplitude of the possible outcomes of measurement but without measurement. An important criterion for a quantum memory is that the efficiency of the recall must exceed 50%. This is the crucial no-cloning limit for security of information, since it guarantees that nobody can access the information by copying it. This benchmark is important because any kind of deterministic amplification of quantum information is fundamentally impossible. On-demand retrieval of information and ability to controllably manipulate the quantum information are also important for quantum applications. When light is absorbed by atoms, it is actually possible to reverse the absorption process. In our memory system: light is absorbed by an ensemble of atoms and, using careful conditioning and control, we can cause the stored light to be regenerated and released at a later time. This is done by applying a gradient of magnetic field along the atomic ensemble that is the basis for our optical memory. To recall the light we flip the sign of the gradient field. This kind of reversible absorption is called photon echo, hence the name of our scheme: The Gradient Echo Memory (GEM). This simple protocol is used in our experiment and can be applied to a range of different atomic systems. We have extended the GEM protocol and experimentally implemented a memory using three-level atoms. We used an off-the-shelf Rb vapour cell operating above room temperature as the memory medium. In this realisation, we broke the efficiency record with 87% recall of the input light pulse. Moreover, through complete state tomography of coherent states we have demonstrated the ability of our memory to noiselessly store quantum states of light. We have also demonstrated that the memory can store a string of pulses and then recall the pulses ondemand in arbitrary order allowing re-sequencing of the stored information. Furthermore, we have shown that pulses could be time-compressed, time-stretched or split into multiple smaller pulses and selectively recalled in several pieces. This technique enables the construction of an optical random-access memory for quantum information. Moreover, the scheme to manipulate the spectral properties of optical data, stored inside the memory, has been introduced. We have also investigated the possibility of obtaining large nonlinear phase shifts between single photons inside the memory. Such strong interactions can be used for the implementation of universal quantum gates.

•Jan 1, 2012•2 citations

Reversible Atomic Memories

A key requirement for quantum information processing applications such as quantum communication or computation is the ability to reliably store, manipulate, and retrieve a piece of information, encoded, for example, in the polarization state of a single photon. Among the many routes presently being explored to achieve these goals is cavity quantum electrodynamics (c-QED), which entails trapping a single atom in a cavity and inducing it to interact with a single photon. In this vein, Boozer et al. show that they are able to imprint the state of a single photon onto a single trapped Cs atom, store it for an appreciable fraction of the lifetime of the atom in the trap, and then retrieve that information again sometime later in the form of another photon and send it on its way. They verify that the whole process is coherent, providing further support for c-QED-based systems as promising candidates for nodes in a quantum information processing network. — ISO

Science•May 25, 2007•0 citations

Control of Photon Storage Time in Photon Echoes using a Deshelving Process

Byoung Seung HAM

Since the first protocol of quantum algorithm was put forth in 1994 (Shor, 1994), quantum information processing has been intensively studied (Nielsen & Chuang, 2000). The quantum approach has benefits over the classical optical information processing in areas such as prime number factorization (Shor, 1994), data searching (Grover, 1996), and highresolution lithography (Boto et al., 2000; Yablonovitch, 1999). Compared to conventional cryptography based on public key cryptosystem (RSA cryptosystem) using conventional computers, prime number factorization using quantum computers has demonstrated a potential for a formidable attack on existing cryptographic systems. Like conventional memory which serves in the information processing unit, such as a processing unit together with logic gates, quantum memory is also essential to quantum information and communications networks. For quantum communications via a classical optical channel, the longest communication distance a quantum light can be transmitted is determined by the sensitivity of optical detectors and a lossy classical channel such as an optical fibre. Based on current technologies, the longest distance a single photon can propagate through an optical fibre is about 100 km (Zbinden et al., 1998). This distance should limit applications of quantum information especially for long-distance quantum communications. To solve the limited photon transmission, a quantum repeater has been introduced for virtually unlimited transmission distance (Duan et al., 2001; Jiang et al., 2007; Simon et al., 2007; Waks et al., 2002). Quantum memory is an essential element for the entangled photon swapping in the quantum repeaters. Because quantum repeaters swap entangled photons shared by neighboring remote quantum nodes in a quantum network, and the quantum information must be kept coherently through the quantum network, the minimum storage time of quantum memory is determined by the longest transmission distance of the lossy optical channel. For tranceatlantic quantum communications, roughly a one-second or more storage time is required. So far, such a long photon storage has not been demonstrated, where conventional quantum memory protocols limit the storage time to spin phase decay time at most (≤10-3 second). Unlike classical memories, quantum memory must satisfy a coherent process. Since the first observation of coherent retrieval of a stored optical pulse in a Bose Einstein condensate using slow light (Liu et al., 2001), interest in quantum memories has increased in the last decade (Alexander et al., 2006; Afzelius et al., 2010; Chaneliere et al., 2005. Choi et al., 2008;

InTech eBooks•Jan 30, 2011•0 citations

Robust quantum memory via quantum control

Andrew D. Greentree, S. G. Schirmer, A. I. Solomon

A general scheme for building a quantum memory by transferring quantum information to an essentially decoherence-free memory transition using quantum control is presented and illustrated by computer simulations.

arXiv:quant-ph/0103118•Mar 20, 2001•1 citation

Robust quantum memory via quantum control

S. G. Schirmer, Andrew D. Greentree, A. I. Solomon

A general scheme for building a quantum memory by transferring quantum information to an essentially decoherence-free memory transition using quantum control is presented and illustrated by computer simulations.

Optical Fiber Communication Conference•Jan 1, 2001•0 citations

Random-access stimulated-echo optical cache memory

Ravinder Kachru, Yu Bai, Xiao A. Shen +1 more

We describe a new approach to develop a high-speed, high-density random access cache memory. This new technique is based on a novel approach using, in essence, a hybrid of the time domain stimulated echo (SE) concept and the frequency domain scheme. It has been demonstrated that the rare-earth doped crystals, can at low temperatures store large amounts of information for up to 24 hours using SE. The basic approach we have developed is the partitioning of the absorption frequency domain into smaller bins, so that each frequency bin stores a smaller portion of information independently. The bins are distinguishable by their different absorption frequencies and they are accessed by changing the laser frequency (color). However, information is still stored and retrieved using the time-domain pulse sequency used in SE. Specifically, with the laser frequency set at the particular absorption of a frequency bin, the laser is externally modulated by an acousto-optic modulator to produce amplitude modulated pulses representing the digital data, the write pulse, and the read pulse, during the write and retrieve operation, respectively. The advantages of this approach are that memory can be stored in space, time, and frequency domain, allowing us to tailor a flexible memory architecture to match those of the computational processor.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Apr 1, 1992•2 citations
Can't quite place a name to the face, or associate a singer with a song? You know, or at least hope, that the information lies intact somewhere in your head, needing only the correct memory trick or stimulus to retrieve it. For quantum communications, where information is transmitted along quantum channels and stored in quantum memories, it is necessary that the stored information be robust and retrievable. However, quantum memories are known to decay because of decoherence, and physicists therefore have to develop their own set of tricks to probe and measure how reliable these memories are. Staudt et al. look at quantum information stored in an optical memory, where the information is encoded in the coherent transfer of the phase and amplitudes of light pulses onto a suitable solid-state medium. They use a photon-echo technique whereby a sequence of pulses initializes the memory cell, encodes the data onto it, and uses a read pulse to generate a stimulated echo pulse which replicates the stored information. The advantage of this scheme is that, though memories may be lost, if they are recalled they remain undistorted. — ISO
The non-interacting and high-speed nature of light makes it an ideal carrier of information that is essential for transmission of quantum information. Indeed, many proposals and demonstrations of quantum cryptography rely on the use of fibre-optic networks. Construction of a memory that can store light and preserve its quantum properties will be useful in a range of quantum information systems such as secure quantum communication and quantum computation. This is why a quantum memory for light is a remarkable objective. The key to quantum memory is to store the probability amplitude of the possible outcomes of measurement but without measurement. An important criterion for a quantum memory is that the efficiency of the recall must exceed 50%. This is the crucial no-cloning limit for security of information, since it guarantees that nobody can access the information by copying it. This benchmark is important because any kind of deterministic amplification of quantum information is fundamentally impossible. On-demand retrieval of information and ability to controllably manipulate the quantum information are also important for quantum applications. When light is absorbed by atoms, it is actually possible to reverse the absorption process. In our memory system: light is absorbed by an ensemble of atoms and, using careful conditioning and control, we can cause the stored light to be regenerated and released at a later time. This is done by applying a gradient of magnetic field along the atomic ensemble that is the basis for our optical memory. To recall the light we flip the sign of the gradient field. This kind of reversible absorption is called photon echo, hence the name of our scheme: The Gradient Echo Memory (GEM). This simple protocol is used in our experiment and can be applied to a range of different atomic systems. We have extended the GEM protocol and experimentally implemented a memory using three-level atoms. We used an off-the-shelf Rb vapour cell operating above room temperature as the memory medium. In this realisation, we broke the efficiency record with 87% recall of the input light pulse. Moreover, through complete state tomography of coherent states we have demonstrated the ability of our memory to noiselessly store quantum states of light. We have also demonstrated that the memory can store a string of pulses and then recall the pulses ondemand in arbitrary order allowing re-sequencing of the stored information. Furthermore, we have shown that pulses could be time-compressed, time-stretched or split into multiple smaller pulses and selectively recalled in several pieces. This technique enables the construction of an optical random-access memory for quantum information. Moreover, the scheme to manipulate the spectral properties of optical data, stored inside the memory, has been introduced. We have also investigated the possibility of obtaining large nonlinear phase shifts between single photons inside the memory. Such strong interactions can be used for the implementation of universal quantum gates.
A key requirement for quantum information processing applications such as quantum communication or computation is the ability to reliably store, manipulate, and retrieve a piece of information, encoded, for example, in the polarization state of a single photon. Among the many routes presently being explored to achieve these goals is cavity quantum electrodynamics (c-QED), which entails trapping a single atom in a cavity and inducing it to interact with a single photon. In this vein, Boozer et al. show that they are able to imprint the state of a single photon onto a single trapped Cs atom, store it for an appreciable fraction of the lifetime of the atom in the trap, and then retrieve that information again sometime later in the form of another photon and send it on its way. They verify that the whole process is coherent, providing further support for c-QED-based systems as promising candidates for nodes in a quantum information processing network. — ISO
Since the first protocol of quantum algorithm was put forth in 1994 (Shor, 1994), quantum information processing has been intensively studied (Nielsen & Chuang, 2000). The quantum approach has benefits over the classical optical information processing in areas such as prime number factorization (Shor, 1994), data searching (Grover, 1996), and highresolution lithography (Boto et al., 2000; Yablonovitch, 1999). Compared to conventional cryptography based on public key cryptosystem (RSA cryptosystem) using conventional computers, prime number factorization using quantum computers has demonstrated a potential for a formidable attack on existing cryptographic systems. Like conventional memory which serves in the information processing unit, such as a processing unit together with logic gates, quantum memory is also essential to quantum information and communications networks. For quantum communications via a classical optical channel, the longest communication distance a quantum light can be transmitted is determined by the sensitivity of optical detectors and a lossy classical channel such as an optical fibre. Based on current technologies, the longest distance a single photon can propagate through an optical fibre is about 100 km (Zbinden et al., 1998). This distance should limit applications of quantum information especially for long-distance quantum communications. To solve the limited photon transmission, a quantum repeater has been introduced for virtually unlimited transmission distance (Duan et al., 2001; Jiang et al., 2007; Simon et al., 2007; Waks et al., 2002). Quantum memory is an essential element for the entangled photon swapping in the quantum repeaters. Because quantum repeaters swap entangled photons shared by neighboring remote quantum nodes in a quantum network, and the quantum information must be kept coherently through the quantum network, the minimum storage time of quantum memory is determined by the longest transmission distance of the lossy optical channel. For tranceatlantic quantum communications, roughly a one-second or more storage time is required. So far, such a long photon storage has not been demonstrated, where conventional quantum memory protocols limit the storage time to spin phase decay time at most (≤10-3 second). Unlike classical memories, quantum memory must satisfy a coherent process. Since the first observation of coherent retrieval of a stored optical pulse in a Bose Einstein condensate using slow light (Liu et al., 2001), interest in quantum memories has increased in the last decade (Alexander et al., 2006; Afzelius et al., 2010; Chaneliere et al., 2005. Choi et al., 2008;
We describe a new approach to develop a high-speed, high-density random access cache memory. This new technique is based on a novel approach using, in essence, a hybrid of the time domain stimulated echo (SE) concept and the frequency domain scheme. It has been demonstrated that the rare-earth doped crystals, can at low temperatures store large amounts of information for up to 24 hours using SE. The basic approach we have developed is the partitioning of the absorption frequency domain into smaller bins, so that each frequency bin stores a smaller portion of information independently. The bins are distinguishable by their different absorption frequencies and they are accessed by changing the laser frequency (color). However, information is still stored and retrieved using the time-domain pulse sequency used in SE. Specifically, with the laser frequency set at the particular absorption of a frequency bin, the laser is externally modulated by an acousto-optic modulator to produce amplitude modulated pulses representing the digital data, the write pulse, and the read pulse, during the write and retrieve operation, respectively. The advantages of this approach are that memory can be stored in space, time, and frequency domain, allowing us to tailor a flexible memory architecture to match those of the computational processor.