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Author  |
Kok, Pieter |
| Title |
Quantum optics: Entangled photons report for duty |
Type |
Journal Article |
| Year |
2010 |
Publication |
Nature Photonics |
Abbreviated Journal |
Nat. Photon. |
| Volume |
4 |
Issue |
8 |
Pages |
504-505 |
| Keywords |
fromIPMRAS |
| Abstract |
Entangled photons are a key ingredient in optical quantum technologies, but researchers have so far been unable to produce a single pair of entangled photons. Now, two groups from China and Austria independently report just that, with a technique that avoids the need to infer entanglement from detection signatures. |
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RPLAB @ gujma @ |
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772 |
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Knee, George C.; Simmons, Stephanie; Gauger, Erik M.; Morton, John J. L.; Riemann, Helge; Abrosimov, Nikolai V.; Becker, Peter; Pohl, Hans-Joachim; Itoh, Kohei M.; Thewalt, Mike L. W.; Briggs, G. Andrew D.; Benjamin, Simon C. |
| Title |
Violation of a Leggett–Garg inequality with ideal non-invasive measurements |
Type |
Journal Article |
| Year |
2012 |
Publication |
Nature Communications |
Abbreviated Journal |
Nat. Comm. |
| Volume |
3 |
Issue |
606 |
Pages |
6 |
| Keywords |
fromIPMRAS |
| Abstract |
The quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test designed by Leggett and Garg can rule out this possibility. The test, originally intended for macroscopic objects, has been implemented in various systems. However to date no experiment has employed the 'ideal negative result' measurements that are required for the most robust test. Here we introduce a general protocol for these special measurements using an ancillary system, which acts as a local measuring device but which need not be perfectly prepared. We report an experimental realization using spin-bearing phosphorus impurities in silicon. The results demonstrate the necessity of a non-classical picture for this class of microscopic system. Our procedure can be applied to systems of any size, whether individually controlled or in a spatial ensemble. |
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RPLAB @ gujma @ |
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767 |
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Kim, Yong-Su; Lee, Jong-Chan; Kwon, Osung; Kim, Yoon-Ho |
| Title |
Protecting entanglement from decoherence using weak measurement and quantum measurement reversal |
Type |
Journal Article |
| Year |
2012 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
| Volume |
8 |
Issue |
2 |
Pages |
117-120 |
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fromIPMRAS |
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Decoherence, often caused by unavoidable coupling with the environment, leads to degradation of quantum coherence. For a multipartite quantum system, decoherence leads to degradation of entanglement and, in certain cases, entanglement sudden death. Tackling decoherence, thus, is a critical issue faced in quantum information, as entanglement is a vital resource for many quantum information applications including quantum computing, quantum cryptography, quantum teleportation and quantum metrology. Here, we propose and demonstrate a scheme to protect entanglement from decoherence. Our entanglement protection scheme makes use of the quantum measurement itself for actively battling against decoherence and it can effectively circumvent even entanglement sudden death. |
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RPLAB @ gujma @ |
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815 |
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Kawano, Yukio; Ishibashi, Koji |
| Title |
An on-chip near-field terahertz probe and detector |
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Journal Article |
| Year |
2008 |
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Nature Photonics |
Abbreviated Journal |
Nature Photon |
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2 |
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10 |
Pages |
618-621 |
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single molecule, terahertz, THz, near-field, microscopy, imaging, 2DEG, GaAs/AlGaAs, detector, applications |
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The advantageous properties of terahertz waves, such as their transmission through objects opaque to visible light, are attracting attention for imaging applications. A promising approach for achieving high spatial resolution is the use of near-field imaging. Although this method has been well established in the visible and microwave regions, it is challenging to perform in the terahertz region. In the terahertz techniques investigated to date, detectors have been located remotely from the probe, which degrades sensitivity, and the influence of far-field waves is unavoidable. Here we present a new integrated detection device for terahertz near-field imaging in which all the necessary detection components — an aperture, a probe and a terahertz detector — are integrated on one semiconductor chip, which is cryogenically cooled. This scheme allows highly sensitive, high-resolution detection of the evanescent field alone and promises new capabilities for high-resolution terahertz imaging. |
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1749-4885 |
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570 |
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Johnson, B. R.; Reed, M. D.; Houck, A. A.; Schuster, D. I.; Bishop, Lev S.; Ginossar, E.; Gambetta, J. M.; Dicarlo, L.; Frunzio, L.; Girvin, S. M.; Schoelkopf, R. J. |
| Title |
Quantum non-demolition detection of single microwave photons in a circuit |
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Journal Article |
| Year |
2010 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
| Volume |
6 |
Issue |
9 |
Pages |
663-667 |
| Keywords |
fromIPMRAS |
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Thorough control of quantum measurement is key to the development of quantum information technologies. Many measurements are destructive, removing more information from the system than they obtain. Quantum non-demolition (QND) measurements allow repeated measurements that give the same eigenvalue. They could be used for several quantum information processing tasks such as error correction, preparation by measurement and one-way quantum computing. Achieving QND measurements of photons is especially challenging because the detector must be completely transparent to the photons while still acquiring information about them. Recent progress in manipulating microwave photons in superconducting circuits has increased demand for a QND detector that operates in the gigahertz frequency range. Here we demonstrate a QND detection scheme that measures the number of photons inside a high-quality-factor microwave cavity on a chip. This scheme maps a photon number, n, onto a qubit state in a single-shot by means of qubit-photon logic gates. We verify the operation of the device for n=0 and 1 by analysing the average correlations of repeated measurements, and show that it is 90% QND. It differs from previously reported detectors because its sensitivity is strongly selective to chosen photon number states. This scheme could be used to monitor the state of a photon-based memory in a quantum computer. |
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RPLAB @ gujma @ |
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806 |
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Ikuta, Rikizo; Kusaka, Yoshiaki; Kitano, suyoshi; Kato, Hiroshi; Yamamoto, Takashi; Koashi, Masato; Imoto, Nobuyuki |
| Title |
Wide-band quantum interface for visible-totelecommunication wavelength conversion |
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Journal Article |
| Year |
2011 |
Publication |
Nature Communications |
Abbreviated Journal |
Nat. Comm. |
| Volume |
2 |
Issue |
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Pages |
5 |
| Keywords |
fromIPMRAS |
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Although near-infrared photons in telecommunication bands are required for long-distance quantum communication, various quantum information tasks have been performed by using visible photons for the past two decades. Recently, such visible photons from diverse media including atomic quantum memories have also been studied. Optical frequency down-conversion from visible to telecommunication bands while keeping the quantum states is thus required for bridging such wavelength gaps. Here we report demonstration of a quantum interface of frequency down-conversion from visible to telecommunication bands by using a nonlinear crystal, which has a potential to work over wide bandwidths, leading to a high-speed interface of frequency conversion. We achieved the conversion of a picosecond visible photon at 780 nm to a 1,522-nm photon, and observed that the conversion process retained entanglement between the down-converted photon and another photon. |
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RPLAB @ gujma @ |
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764 |
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Hosseini, M.; Campbell, G.; Sparkes, B. M.; Lam, P. K.; Buchler, B. C. |
| Title |
Unconditional room-temperature quantum memory |
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Journal Article |
| Year |
2011 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
| Volume |
7 |
Issue |
10 |
Pages |
794-798 |
| Keywords |
fromIPMRAS |
| Abstract |
Just as classical information systems require buffers and memory, the same is true for quantum information systems. The potential that optical quantum information processing holds for revolutionizing computation and communication is therefore driving significant research into developing optical quantum memory. A practical optical quantum memory must be able to store and recall quantum states on demand with high efficiency and low noise. Ideally, the platform for the memory would also be simple and inexpensive. Here, we present a complete tomographic reconstruction of quantum states that have been stored in the ground states of rubidium in a vapour cell operating at around 80 °C. Without conditional measurements, we show recall fidelity up to 98% for coherent pulses containing around one photon. To unambiguously verify that our memory beats the quantum no-cloning limit we employ state-independent verification using conditional variance and signal-transfer coefficients. |
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RPLAB @ gujma @ |
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824 |
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| Author |
Home, Jonathan |
| Title |
Quantum entanglement: Watching correlations disappear |
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Journal Article |
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2010 |
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Nature Physics |
Abbreviated Journal |
Nat. Phys. |
| Volume |
6 |
Issue |
12 |
Pages |
938-939 |
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fromIPMRAS |
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Engineered decoherence enables tracking of multipartite entanglement as a quantum state decays. |
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RPLAB @ gujma @ |
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832 |
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| Author |
Hollenberg, Lloyd C. L. |
| Title |
Quantum control: Through the quantum chicane |
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Journal Article |
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2012 |
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Nature Physics |
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Nat. Phys. |
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8 |
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2 |
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113-114 |
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fromIPMRAS |
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In quantum control there is an inherent tension between high fidelity requirements and the need for speed to avoid decoherence. A direct comparison of quantum control protocols at these two extremes indicates where the sweet spot may lie. |
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RPLAB @ gujma @ |
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812 |
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He, Rongrui; Sazio, Pier J. A.; Peacock, Anna C.; Healy, Noel; Sparks, Justin R.; Krishnamurthi, Mahesh; Gopalan, Venkatraman; Badding, John V. |
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Integration of gigahertz-bandwidth semiconductor devices inside microstructured optical fibres |
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Journal Article |
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2012 |
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Nature Photonics |
Abbreviated Journal |
Nat. Photon. |
| Volume |
6 |
Issue |
3 |
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174-179 |
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fromIPMRAS |
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The prospect of an all-fibre optical communications network in which light can be generated, modulated and detected within the fibre itself without the need for discrete optoelectronic devices is an appealing one. However, to become a reality, this approach requires the incorporation of optoelectronic materials and functionalities into silica fibres to create a new breed of semiconductor-fibre hybrid devices for performing various tasks. Here, we report the integration of precisely doped semiconductor materials and high-quality rectifying semiconductor junctions into microstructured optical fibres, enabling high-speed, in-fibre functionalities such as photodetection at telecommunications wavelengths. These semiconductor-fibre hybrid devices exhibit a bandwidth of up to 3 GHz and seamless coupling to standard single-mode optical fibres. |
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RPLAB @ gujma @ |
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783 |
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