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Proceedings ArticleDOI

Periodic single-photon source and quantum memory

03 Feb 2004-Vol. 5161, pp 57-65
TL;DR: In this article, a recent experimental demonstration of a periodic single-photon source based on parametric down-conversion photon pairs, optical storage loops, and high-speed switching is presented.
Abstract: Although there has been tremendous progress in the development of true “on-demand” single-photon sources, periodic or “pseudodemand” single-photon sources can be a sufficient resource for many optical quantum information processing applications. Here we review a recent experimental demonstration of a periodic single-photon source based on parametric down-conversion photon pairs, optical storage loops, and high-speed switching. We also review an experiment in which high speed switching and storage loops were used to implement a periodic quantum memory device for polarization-encoded single-photon qubits. Finally, we describe a method in which two of these periodic quantum memory devices are used to facilitate the production of a periodic source of entangled photon pairs. These experiments and proposals are all motivated within the context of linear optics quantum computing.

Summary (1 min read)

2. PERIODIC SINGLE-PHOTON SOURCE

  • It should be noted that the heralding efficiencies in parametric down-conversion can be quite high.
  • The authors current experimental efforts involve constructing two of these periodic sources, and demonstrating higherorder interference effects among the single-photons emitted from them.
  • The required mode-matching of these independent photon sources is being accomplished through the use of single-mode optical fibers for spatial mode-matching, as well as temporal mode-matching through the use of ultra-short pulsed-pump down-conversion and narrow-band spectral filtering as used, for example, in quantum teleportation experiments.
  • 16 Even with the additional parametric down-conversion phase-matching complications arising from the use of femtosecond pumping pulses, and the restrictions of coupling light into single-mode fibers, the authors have recently achieved heralding efficiencies higher than 50% using variations on the coupling techniques described by Weinfurter's group.

3. CYCLICAL QUANTUM MEMORY DEVICE

  • In analogy with the periodic single-photon source results of Figure 4 , the upper row of Figure 6 demonstrates the ability to store and switch out the photons after some chosen number of cycles.
  • For each of the plots in the upper row, the corresponding plot in the lower row shows the results of measuring the polarization state (eg. qubit value) with a polarization analyzer.
  • The results clearly showed the expected Cosine-squared signature of the 30 o linear polarization state for photons stored an odd number of cycles, and the expected 60 o linear polarization state (eg. bit-flipped value) for photons stored an even number of cycles.

4. PERIODIC ENTANGLED PHOTON-PAIR SOURCE

  • Whereas loss in either of the CQM's will cause an obvious reduction in the quality of the stored and released entangled state, the effects of phase shifts between the two devices are not as detrimental.
  • Overall phase shifts between the two devices essentially factor out of the two-photon state in such a way that phase-locking of the two memory loops is not required to maintain the coherence of the stored Bell state.
  • Fortunately, as described in Section 3, the CQM's are (in principle) immune to these phase shifts for pairs stored an even number of cycles.

5. SUMMARY

  • The authors recent demonstrations of a periodic single-photon source 11 and cyclical quantum memory for singlephoton qubits 12 were of a proof-of-principle nature, and suffered from relatively large sources of errors.
  • Both of these periodic devices suffered from losses on the order of 20% per round trip, which is clearly insufficient for a practical realization of applications such as the proposed method of producing a periodic source of entangled photon pairs.

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PROCEEDINGS OF SPIE
SPIEDigitalLibrary.org/conference-proceedings-of-spie
Periodic single-photon source and
quantum memory
Pittman, Todd, Fitch, Michael, Jacobs, Bryan, Franson,
James
Todd B. Pittman, Michael J. Fitch, Bryan C. Jacobs, James D. Franson,
"Periodic single-photon source and quantum memory," Proc. SPIE 5161,
Quantum Communications and Quantum Imaging, (3 February 2004); doi:
10.1117/12.504887
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003,
San Diego, California, United States
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Periodic Single-Photon Source and Quantum Memory
T.B. Pittman, M.J. Fitch, B.C. Jacobs, and J.D. Franson
Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723
ABSTRACT
Although there has been tremendous progress in the development of true “on-demand” single-photon sources,
periodic or “pseudodemand” single-photon sources can be a sufficient resource for many optical quantum infor-
mation processing applications. Here we review a recent experimental demonstration of a periodic single-photon
source based on parametric down-conversion photon pairs, optical storage loops, and high-speed switching. We
also review an experiment in which high speed switching and storage loops were used to implement a periodic
quantum memory device for polarization-encoded single-photon qubits. Finally, we describe a method in which
two of these periodic quantum memory devices are used to facilitate the production of a periodic source of
entangled photon pairs. These experiments and proposals are all motivated within the context of linear optics
quantum computing.
Keywords: single photon, quantum memory, linear optics, parametric down-conversion
1. INTRODUCTION
The recent development of linear optics quantum computing (LOQC) by Knill, LaFlamme, and Milburn (KLM)
1
has led to a renewed interest in optical approaches to quantum information processing.
2
Although significant
innovations will be required for a full scale linear optics quantum computer,
1, 3–5
useful small-scale devices
based on simple linear optics quantum gates
6–9
appear to be within the reach of near-term technology.
10
One
of the primary resources required for quantum devices of this kind are large numbers of highly synchronized
indistinguishable single-photon states. At the present time, it seems likely that this will involve the use of a
master laser pulse train (such as that produced by a mode-locked laser) to provide a natural clock-cycle for the
resource production and logic gate operations.
In such a periodic system, true “push-button” sources capable of emitting single photons at arbitrary times
are not required; rather, it is sufficient to have periodic photon resources that are only capable of releasing single-
photons at well-defined time intervals corresponding to the clock-cycle. This represents a significant relaxation
on the requirements of the photon sources and, as will be shown below, even allows the use of photon sources
that are inherently random. In addition to periodic single-photon sources,
11
periodic short-term quantum
memories
12
and periodic sources of entangled photon pairs
13
can also be extremely valuable. In this paper we
review several proof-of-principle experiments and proposals along these lines. The common theme is the use of
high-speed switches and simple optical storage loops designed to match the clock-cycle of an envisioned circuit
of linear optics quantum gates.
To understand the use of these periodic resources, we first provide an overview of a single linear optics
quantum gate,
1
such as the controlled-NOT (CNOT) gate,
2
shown in Figure 1. In contrast to an optical CNOT
gate based on direct nonlinear couplings between the control and target photons (Figure 1(a)), the required
nonlinearity of the linear optics gate illustrated in Figure 1(b) is obtained by mixing the inputs with N ancilla
photons in a “black box” containing only linear optical elements, and then measuring the state of the ancilla
photons after the interaction. Because the state reduction and measurement process is inherently nonlinear,
it can be used to project out the desired logical output state when certain measurement results are obtained.
Linear optics gates of this kind are therefore probabilistic, in that the correct logical output is signalled by
specific measurement results which only occur some fraction of the time. However, the success rate of these gates
can approach unity with sufficient resources; it has been shown the failure rate can scale as
1
N
or
1
N
2
depending
on the specific approach that is used.
1, 3
The use of periodic resources in such a linear optics gate is illustrated in Figure 2. In this example, each of
the N ancilla photons is supplied by a periodic source consisting of a storage loop and switch (labelled S). The
Quantum Communications and Quantum Imaging, edited by Ronald E. Meyers, Yanhua Shih,
Proc. of SPIE Vol. 5161 (SPIE, Bellingham, WA, 2004) · 0277-786X/04/$15 · doi: 10.1117/12.504887
57
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output
control
photon
target
photon
12 N
….
D
1
D
2
D
N
….
“Black Box”
(only linear optics)
(b) linear optics gate
output
control
photon
target
photon
“Black Box”
(nonlinear coupling)
(a) nonlinear optics gate
ancilla photons
Figure 1. The basic idea of a two-qubit linear optics quantum gate. (a) illustrates a “traditional” controlled-NOT gate
based on direct nonlinear couplings between the control and target photon qubits. (b) illustrates a probabilistic linear
optics controlled-NOT gate,
1
in which the required nonlinearity is essentially obtained by mixing the control and target
qubits with N ancilla qubits, and then making projective measurements with a series of N ideal single-photon detectors.
photons themselves are produced and heralded by low-efficiency random sources that are driven by the master
laser pulse train, causing the various storage loops to become occupied with their single photons at potentially
different intervals (for example, ancilla source 2 becomes occupied one period later than ancilla source 1 in the
figure).
The basic idea is to start the entire ancilla generation process a sufficiently large number of cycles in advance of
the pre-arranged gate operation time so that, with high probability, each of the N storage loops will be occupied
with a single photon before the gate operation time. The N ancilla photons can then be simultaneously switched
into the linear optics gate at the appropriate time. One subtlety of the particular gate illustrated in Figure 2 is
that the N ancilla photons are not entangled. However, gates of this kind can be used to non-deterministically
produce the specific entangled states required to implement high-fidelity linear optics logic gates.
3, 5
This type
of “bootstrapping” of single-photon resources is a basic feature of linear optics quantum computing.
1
The other type of periodic device shown in Figure 2 is a periodic (or cyclical) quantum memory, which is
placed in each of the control and target photon input modes. The cyclical quantum memories (CQM’s) are also
based on storage loops and switches, and are capable of storing the qubits without measuring or altering their
S S S
CQM
CQM
control
photon
target
photon
12 N
..…
D
1
D
2
D
N
output
“Black Box”
(only linear optics)
..…
Figure 2. A linear optics quantum gate using periodic resources. Each of the N ancilla photons is supplied by a periodic
photon source consisting of storage loop and switch (labelled S), while the input control and target photon qubits can be
stored in cyclical quantum memory devices (CQM).
58 Proc. of SPIE Vol. 5161
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states. These CQM’s would be particularly useful in a circuit where, for example, the input qubits are delivered
to the logic gate a few cycles before the pre-arranged gate operation time.
We have recently performed proof-of-principle experimental demonstrations of periodic resources of the kind
illustrated in Figure 2. In Section 2, we will review the demonstration of a periodic single-photon source
where the single-photons were heralded from parametric down-conversion pairs and the real-time switching was
accomplished with a high-speed Pockels cell.
11
In Section 3, we will review the results of a demonstration of a
cyclical quantum memory (CQM) device using much of the same technology.
12
As will be seen, this CQM has
a number of interesting features, including a natural resistance to a certain class of single-qubit errors. Finally,
in Section 4 we highlight a recent proposal
13
to use two of these CQM’s along with linear optics quantum logic
gates to produce a periodic source of entangled photon pairs, which is another valuable resource in a number of
optical quantum information applications.
2. PERIODIC SINGLE-PHOTON SOURCE
A simplified schematic of our periodic photon source is shown in Figure 3. Here a parametric down-conversion
crystal (PDC) is pumped by a train of ultra-short laser pulses with a repetition rate of τ
1
. Within the context
of the periodic linear optics quantum gate of Figure 2, this pulse train is derived from the master laser, and τ
is defined as the system’s cycle-time.
Although parametric down-conversion is an inherently random process, the use of a pulsed pumping train
restricts the possible pair emission time to one of the short intervals separated by τ. The pumping power
is assumed to be sufficiently low that the probability of producing a pair during a given pump pulse is much
less than one. However, when a pair is actually produced, the detection of one member of the pair is used to
activate an electro-optic (EO) switch that re-routes the twin photon into the storage loop, and prevents any
further photons from being stored. The stored single-photon is then known to be circulating in the loop, and
can be switched out at a later cycle.
In this low-power pumping regime, the errant probability of producing more than one pair per pulse would
be negligible and, in principle, could be definitively projected out by the use of an ideal photon-number resolving
detector.
14, 15
In our experiment,
11
the switch was constructed of a polarizing beam splitter, and a Pockels cell (EO
device) that was used to rotate the polarization of the twin photon as needed to store or release it from the
loop. The storage loop itself was a 4 meter free-space loop, providing a value of τ = 13ns. Although the
original experiments were actually completed with a cw pumping laser, this value of τ was chosen to match
the repetition rate of a master laser pulse train obtained from a standard 76MHz mode-locked Ti:Sapphire laser
being used in our current experiments. The switching speed was dictated by the rise-time of the Pockels cell,
which was roughly 10ns. Results from that experiment are summarized in Figure 4. The data shows the ability
PDC
EO
SWITCH
output
storage
loop
τ
τ
detector
Figure 3. A simplified schematic of our periodic “pseudodemand” source of single-photons.
11
A parametric down-
conversion crystal (PDC) is pumped by a low-power laser pulse train providing a source cycle-time of τ . When a photon
pair is actually produced, the detection of one of the photons activates an electro-optic (EO) switch that is used to re-route
the twin photon into a storage loop. The stored photon can then be switched out after some number of cycles.
Proc. of SPIE Vol. 5161 59
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Citations
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Abstract: The maturation of many photonic technologies from individual components to next-generation system-level circuits will require exceptional active control of complex states of light. A prime example is in quantum photonic technology: while single-photon processes are often probabilistic, it has been shown in theory that rapid and adaptive feedforward operations are sufficient to enable scalability. Here, we use simple “off-the-shelf” optical components to demonstrate active multiplexing—adaptive rerouting to single modes—of eight single-photon “bins” from a heralded source. Unlike other possible implementations, which can be costly in terms of resources or temporal delays, our new configuration exploits the benefits of both time and space degrees of freedom, enabling a significant increase in the single-photon emission probability. This approach is likely to be employed in future near-deterministic photon multiplexers with expected improvements in integrated quantum photonic technology.

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TL;DR: The experimental demonstration of two logic devices of this kind, a destructive controlled-NOT gate and a quantum parity check are reported, using polarization-encoded qubits incident on a polarizing beam splitter.
Abstract: Summary form only given. Knill, Laflamme, and Milburn (2001) showed that probabilistic quantum logic devices could be implemented using only linear optical elements, additional ancilla photons, and post-selection based on the output of single-photon detectors. These devices produce the desired result with certainty when a specific output from the detectors is obtained, but that will only occur for some fraction of the events. Here we report the experimental demonstration of two logic devices of this kind, a destructive controlled-NOT gate and a quantum parity check. In each of these devices, two polarization-encoded qubits in the form of two single photons from a parametric down-conversion source are incident on a polarizing beam splitter.

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Abstract: Photonic qubits constitute a leading platform to disruptive quantum technologies due to their unique low-noise properties. The cost of the photonic approach is the non-deterministic nature of many of the processes, including single-photon generation, which arises from parametric sources and negligible interaction between photons. Active temporal multiplexing - repeating a generation process in time and rerouting to single modes using an optical switching network - is a promising approach to overcome this challenge and will likely be essential for large-scale applications with greatly reduced resource complexity and system sizes. Requirements include the precise synchronization of a system of low-loss switches, delay lines, fast photon detectors, and feed-forward. Here we demonstrate temporal multiplexing of 8 'bins' from a double-passed heralded photon source and observe an increase in the heralding and heralded photon rates. This system points the way to harnessing temporal multiplexing in quantum technologies, from single-photon sources to large-scale computation.

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Cites background from "Periodic single-photon source and q..."

  • ...Temporal has been proposed for single-photon [7, 8] and entangled state generation [7, 9, 14, 20], as well as for photon memories [9] and boson sampling schemes [21]....

    [...]

Proceedings ArticleDOI
19 Oct 2004
TL;DR: In this article, an experimental demonstration of a simple irreversible circuit of two probabilistic exclusive-OR (XOR) gates for single-photon qubits is presented, and the operation of the individual linear-optics gates and the overall circuit in terms of two-and threephoton quantum interference effects are described.
Abstract: We review an experimental demonstration of a simple irreversible circuit of two probabilistic exclusive-OR (XOR) gates for single-photon qubits. We describe the operation of the individual linear-optics gates and the overall circuit in terms of two-photon and three-photon quantum interference effects. We also discuss future plans for quantum circuits using single-photon qubits from stored parametric down-conversion sources.
References
More filters
Journal ArticleDOI
04 Jan 2001-Nature
TL;DR: It is shown that efficient quantum computation is possible using only beam splitters, phase shifters, single photon sources and photo-detectors and are robust against errors from photon loss and detector inefficiency.
Abstract: Quantum computers promise to increase greatly the efficiency of solving problems such as factoring large integers, combinatorial optimization and quantum physics simulation. One of the greatest challenges now is to implement the basic quantum-computational elements in a physical system and to demonstrate that they can be reliably and scalably controlled. One of the earliest proposals for quantum computation is based on implementing a quantum bit with two optical modes containing one photon. The proposal is appealing because of the ease with which photon interference can be observed. Until now, it suffered from the requirement for non-linear couplings between optical modes containing few photons. Here we show that efficient quantum computation is possible using only beam splitters, phase shifters, single photon sources and photo-detectors. Our methods exploit feedback from photo-detectors and are robust against errors from photon loss and detector inefficiency. The basic elements are accessible to experimental investigation with current technology.

5,236 citations

Journal ArticleDOI
TL;DR: This work gives the conditions for high fringe visibility and particle collection efficiency as required for a Bell test and subcoherence-time monitoring of the idlers provides a noninteractive quantum measurement entangling and preselecting the independent signals without touching them.
Abstract: Using independent sources one can realize an ``event-ready'' Bell--Einstein-Podolsky-Rosen experiment in which one can measure directly the probabilities of the various outcomes including nondetection of both particles. Our proposal involves two parametric down-converters. Subcoherence-time monitoring of the idlers provides a noninteractive quantum measurement entangling and preselecting the independent signals without touching them. We give the conditions for high fringe visibility and particle collection efficiency as required for a Bell test.

1,636 citations

Journal ArticleDOI
TL;DR: In this paper, the operation of several quantum logic operations of an elementary nature, including a quantum parity check and a quantum encoder, and how they may be combined to implement a controlled-NOT (CNOT) gate are described.
Abstract: It has previously been shown that probabilistic quantum logic operations may be performed using linear optical elements, additional photons (ancilla), and post-selection based on the output of single-photon detectors. Here we describe the operation of several quantum logic operations of an elementary nature, including a quantum parity check and a quantum encoder, and we show how they may be combined to implement a controlled-NOT (CNOT) gate. All of these gates may be constructed using polarizing beam splitters that completely transmit one state of polarization and totally reflect the orthogonal state of polarization, which allows a simple explanation of each operation. We also describe a polarizing beam splitter implementation of a CNOT gate that is closely analogous to the quantum teleportation technique previously suggested by Gottesman and Chuang [Nature 402, 390 (1999)]. Finally, our approach has the interesting feature that it makes practical use of a quantum-eraser technique.

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"Periodic single-photon source and q..." refers methods in this paper

  • ...For example, the enlarged view of the CNOT gate within the dashed box of Figure 7 shows the use of our previously proposed probabilistic CNOT gate which uses two polarizing beam splitters and an ancilliary pair of entangled photons.(7) The use of a probabilistic linear optics CNOT gate (as opposed to a deterministic one) in this protocol will reduce the rate at which entangled pairs are heralded but, at least in principle, will not affect their quality....

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  • ...In this scenario the CNOT gate can be probabilistic, and the expanded view of the dashed box shows the use of our proposed linear optics CNOT gate based on polarizing beam splitters.(7) The required values of the detected qubits are described in the text....

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Abstract: Photon-number-resolving detectors are needed for a variety of applications including linear-optics quantum computing. Here we describe the use of time-multiplexing techniques that allow ordinary single-photon detectors, such as silicon avalanche photodiodes, to be used as photon-number-resolving detectors. The ability of such a detector to correctly measure the number of photons for an incident number state is analyzed. The predicted results for an incident coherent state are found to be in good agreement with the results of a proof-of-principle experimental demonstration.

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Abstract: Probabilistic quantum nondemolition (QND) measurements can be performed using linear optics and postselection. Here we show how QND devices of this kind can be used in a straightforward way to implement a quantum relay, which is capable of extending the range of a quantum cryptography system by suppressing the effects of detector noise. Unlike a quantum repeater, a quantum relay system does not require entanglement purification or the ability to store photons.

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Frequently Asked Questions (1)
Q1. What have the authors contributed in "Periodic single-photon source and quantum memory" ?

Here the authors review a recent experimental demonstration of a periodic single-photon source based on parametric down-conversion photon pairs, optical storage loops, and high-speed switching. The authors also review an experiment in which high speed switching and storage loops were used to implement a periodic quantum memory device for polarization-encoded single-photon qubits. Finally, the authors describe a method in which two of these periodic quantum memory devices are used to facilitate the production of a periodic source of entangled photon pairs.