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| Author |
Gustafsson, Martin V.; Santos, Paulo V.; Johansson, Göran; Delsing, Per |
| Title |
Local probing of propagating acoustic waves in a gigahertz echo chamber |
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Journal Article |
| Year |
2012 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
| Volume |
8 |
Issue |
4 |
Pages |
338-343 |
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fromIPMRAS |
| Abstract |
In the same way that micro-mechanical resonators resemble guitar strings and drums, surface acoustic waves resemble the sound these instruments produce, but moving over a solid surface rather than through air. In contrast with oscillations in suspended resonators, such propagating mechanical waves have not before been studied near the quantum mechanical limits. Here, we demonstrate local probing of surface acoustic waves with a displacement sensitivity of 30amRMSHz-1/2 and detection sensitivity on the single-phonon level after averaging, at a frequency of 932MHz. Our probe is a piezoelectrically coupled single-electron transistor, which is sufficiently fast, non-destructive and localized to enable us to track pulses echoing back and forth in a long acoustic cavity, self-interfering and ringing the cavity up and down. We project that strong coupling to quantum circuits will enable new experiments, and hybrids using the unique features of surface acoustic waves. Prospects include quantum investigations of phonon-phonon interactions, and acoustic coupling to superconducting qubits for which we present favourable estimates. |
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813 |
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Korotkov, Alexander N. |
| Title |
Entanglement preservation: The Sleeping Beauty approach |
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Journal Article |
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2012 |
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Nature Physics |
Abbreviated Journal |
Nat. Phys. |
| Volume |
8 |
Issue |
2 |
Pages |
107-108 |
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fromIPMRAS |
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Two-qubit entanglement can be preserved by partially measuring the qubits to leave them in a 'lethargic' state. The original state is restored using quantum measurement reversal after the qubits have travelled through a decoherence channel. |
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814 |
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Kim, Yong-Su; Lee, Jong-Chan; Kwon, Osung; Kim, Yoon-Ho |
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Protecting entanglement from decoherence using weak measurement and quantum measurement reversal |
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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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815 |
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Bason, Mark G.; Viteau, Matthieu; Malossi, Nicola; Huillery, Paul; Arimondo, Ennio; Ciampini, Donatella; Fazio, Rosario; Giovannetti, Vittorio; Mannella, Riccardo; Morsch, Oliver |
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High-fidelity quantum driving |
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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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147-152 |
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fromIPMRAS |
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Accurately controlling a quantum system is a fundamental requirement in quantum information processing and the coherent manipulation of molecular systems. The ultimate goal in quantum control is to prepare a desired state with the highest fidelity allowed by the available resources and the experimental constraints. Here we experimentally implement two optimal high-fidelity control protocols using a two-level quantum system comprising Bose-Einstein condensates in optical lattices. The first is a short-cut protocol that reaches the maximum quantum-transformation speed compatible with the Heisenberg uncertainty principle. In the opposite limit, we realize the recently proposed transitionless superadiabatic protocols in which the system follows the instantaneous adiabatic ground state nearly perfectly. We demonstrate that superadiabatic protocols are extremely robust against control parameter variations, making them useful for practical applications. |
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RPLAB @ gujma @ |
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816 |
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Pernice, W.; Schuck, C.; Minaeva, O.; Li, M.; Goltsman, G. N.; Sergienko, A. V.; Tang, H. X. |
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High speed and high efficiency travelling wave single-photon detectors embedded in nanophotonic circuits |
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Miscellaneous |
| Year |
2012 |
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arXiv |
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arXiv |
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1108.5299 |
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1-23 |
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optical waveguides, waveguide SSPD, guantum photonics, jitter, detection efficiency |
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Ultrafast, high quantum efficiency single photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. High photon detection efficiency is essential for scalable measurement-based quantum computation, quantum key distribution, and loophole-free Bell experiments. However, imperfect modal matching and finite photon absorption rates have usually limited the maximum attainable detection efficiency of single photon detectors. Here we demonstrate a superconducting nanowire detector atop nanophotonic waveguides which allows us to drastically increase the absorption length for incoming photons. When operating the detectors close to the critical current we achieve high on-chip single photon detection efficiency up to 91% at telecom wavelengths, with uncertainty dictated by the variation of the waveguide photon flux. We also observe remarkably low dark count rates without significant compromise of detection efficiency. Furthermore, our detectors are fully embedded in a scalable silicon photonic circuit and provide ultrashort timing jitter of 18ps. Exploiting this high temporal resolution we demonstrate ballistic photon transport in silicon ring resonators. The direct implementation of such a detector with high quantum efficiency, high detection speed and low jitter time on chip overcomes a major barrier in integrated quantum photonics. |
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845 |
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