Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session V44: Quantum Information and CommunicationFocus
|
Hide Abstracts |
Sponsoring Units: GQI Chair: Mark Wilde, Louisiana State University Room: 347 |
Thursday, March 17, 2016 2:30PM - 3:06PM |
V44.00001: Second-Order Asymptotics for the Classical Capacity of Image-Additive Quantum Channels Invited Speaker: Marco Tomamichel We study non-asymptotic fundamental limits for transmitting classical information over memoryless quantum channels, i.e. we investigate the amount of classical information that can be transmitted when a quantum channel is used a finite number of times and a fixed, non-vanishing average error is permissible. Specifically we consider the classical capacity of quantum channels that are image-additive, including all classical to quantum channels, as well as the product state capacity of arbitrary quantum channels. In both cases we show that the non-asymptotic fundamental limit admits a second-order approximation that illustrates the speed at which the rate of optimal codes converges to the Holevo capacity as the blocklength tends to infinity. The behavior is governed by a new channel parameter, called channel dispersion, for which we provide a geometrical interpretation. [Preview Abstract] |
Thursday, March 17, 2016 3:06PM - 3:42PM |
V44.00002: Quantum Coding with Finite Resources Invited Speaker: Mario Berta The quantum capacity of a memoryless channel determines the maximal rate at which we can code reliably over asymptotically many uses of the channel. Here we argue that this asymptotic characterization is often insufficient in practice where decoherence severely limits our ability to manipulate large quantum systems in the encoder and decoder. For all practical purposes we should instead focus on the optimal trade-off between three parameters: the rate of the code, the size of the quantum devices at the encoder and decoder, and the fidelity of the transmission. Towards this goal, we find approximate and exact characterizations of this tradeoff for various channels, including dephasing, depolarizing and erasure channels. In each case the tradeoff is parametrized by the capacity and a second channel parameter, the quantum channel dispersion. In the process we develop several general bounds that are valid for all finite-dimensional quantum channels and can be computed efficiently. [Preview Abstract] |
Thursday, March 17, 2016 3:42PM - 3:54PM |
V44.00003: Experimental loophole-free Bell inequality violation using electron spins separated by 1.3 km B Hensen, H Bernien, A E Dr\'{e}au, A Reiserer, N Kalb, M S Blok, J Ruitenberg, R F L Vermeulen, R N Schouten, C Abell\'{a}n, W Amaya, V Pruneri, M W Mitchell, M Markham, D J Twitchen, D Elkous, S Wehner, T H Taminiau, R Hanson 50 years ago[1], John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory. Numerous Bell inequality tests have been reported, however, all experiments reported so far required additional assumptions to obtain a contradiction with local realism, resulting in loopholes. Here we will present[2] a Bell experiment that is free of any such additional assumption. We use an event-ready scheme that enables the generation of robust entanglement between distant electron spins. Efficient spin read-out avoids the fair-sampling assumption, while the use of fast random-basis selection and spin read-out combined with a spatial separation of 1.3 km ensure the required locality conditions. We performed 245 trials that tested the CHSH--Bell inequality S$\le $2 and found S$=$2.42$+$-0.20. A null-hypothesis test yields a probability of P$\le $0.039 that a local-realist model for space-like separated sites could produce data with a violation at least as large as we observe, even when allowing for memory in the devices. [1] J.S. Bell, Physics 1, 195-200, (1964) [2] Hensen et al. Nature 526, 682 (2015) [Preview Abstract] |
Thursday, March 17, 2016 3:54PM - 4:06PM |
V44.00004: Beating the Classical Limits of Information Transmission using a Quantum Decoder Akib Karim, Zixin Huang, Rob Chapman, Marco Tomamichel, Steve Flammia, Alberto Peruzzo Reliable transmission of information over a noisy channel is a fundamental challenge in communication theory. The emergence of quantum technologies has created a new class of strategies that allow for message recovery greater than purely classical methods. Despite this, for minimal uses of the channel, finding such schemes remains a challenge. We investigate the amplitude damping channel which describes physical systems that suffer energy loss such as in cavity quantum electrodynamics or spin chain excitations. We derive and experimentally demonstrate the fundamental limit for message recovery possible with only classical methods. We then propose a quantum decoder and experimentally demonstrate message recovery past this classical limit. We use polarisation-encoded photonic qubits. The post-amplitude damping states are generated by an unbalanced Mach-Zehnder interferometer and entanglement is accomplished with a linear optical probabilistic controlled z gate. Our quantum decoder uses a single entangling gate at the receiver where other similar schemes rely on both the sender and the receiver having quantum devices. Our results present an advance in discovering the quantum capabilities of finite resource communications, with specific regard to the amplitude damping channel. [Preview Abstract] |
Thursday, March 17, 2016 4:06PM - 4:18PM |
V44.00005: Quantum Key Distribution based on Silicon Integrated Photonic Devices Darius Bunandar, Nicholas Harris, Zheshen Zhang, Ran Ding, Tom Baehr-Jones, Michael Hochberg, Jeffrey Shapiro, Franco Wong, Dirk Englund We present a compact quantum key distribution (QKD) transmitter near a 1550-nm wavelength using microring modulators implemented on a silicon-on-insulator photonics platform. The transmitter generates time-bin based qubits with a temporal FWHM of 940~ps and an extinction ratio beyond 16~dB. We prove the feasibility of the transmitter with a coherent one-way QKD protocol, where the bit string is encoded in the arrival time of the time-bin qubits and possible eavesdropping is monitored via the intereference visibility of neighboring time-bin qubits~\footnote{B. Korzh, C. C. W. Lim, R. Houlmann, N. Gisin, M. J. Li, D. Nolan, B. Sanguinetti, R. Thew, and H. Zbinden, Nature Photonics \textbf{9}, 163--168 (2015)}. The receiver consists of an asymmetric beamsplitter, which provides a random choice of measurement basis, followed by either a superconducting nanowire single-photon detector (SNSPD) or an unbalanced Michelson interferometer with SNSPDs. This experiment demonstrates the feasibility of high-speed QKD based on CMOS-compatible silicon photonics integrated circuits. [Preview Abstract] |
Thursday, March 17, 2016 4:18PM - 4:30PM |
V44.00006: Quantum Versus Classical Advantages in Secret Key Distillation (and Their Links to Quantum Entanglement Eric Chitambar, Benjamin Fortescue, Min-Hsiu Hsieh We consider the extraction of shared secret key from correlations that are generated by either a classical or quantum source. In the classical setting, two honest parties (Alice and Bob) use public discussion and local operations to distill secret key from some distribution $p_{XYZ}$ that is shared with an unwanted eavesdropper (Eve). In the quantum settings, the correlations $p_{XYZ}$ are delivered to the parties as either an incoherent mixture of orthogonal quantum states or as coherent superposition of such states. Here we demonstrate that the classical and quantum key rates are equivalent when the correlations are generated incoherently in the quantum setting. For coherent sources, we next show that the rates are incomparable, and in fact, their difference can be arbitrarily large in either direction. However, we identify a large class of non-trivial distributions that possess the following properties: (i) Eve's advantage is always greater in the quantum source than classically, and (ii) for the entanglement shared in the coherent source, the so-called entanglement cost/squashed entanglement/relative entropy of entanglement can all be computed. We thus present a rare instance in which various entropic entanglement measures of a quantum state can be explicitly computed. [Preview Abstract] |
Thursday, March 17, 2016 4:30PM - 4:42PM |
V44.00007: Unstructured quantum key distribution Patrick Coles, Eric Metodiev, Norbert Lutkenhaus Quantum key distribution (QKD) allows for communication with security guaranteed by quantum theory. The main theoretical problem in QKD is to calculate the secret key rate for a given protocol. Analytical formulas are known for protocols with a high degree of symmetry, since symmetry simplifies the analysis. However, experimental imperfections break symmetries, hence the effect of imperfections on key rates is difficult to estimate. Furthermore, it is an interesting question whether (intentionally) asymmetric protocols could outperform symmetric ones. In this work, we develop a robust numerical approach for calculating the key rate for arbitrary discrete-variable QKD protocols. Ultimately this will allow researchers to study ``unstructured'' protocols, i.e., those that lack symmetry. Our approach relies on transforming the key rate calculation to the dual optimization problem, which dramatically reduces the number of parameters and hence the calculation time. We illustrate our method by investigating some unstructured protocols for which the key rate was previously unknown. [Preview Abstract] |
Thursday, March 17, 2016 4:42PM - 4:54PM |
V44.00008: A Contextuality Based Quantum Key Distribution Protocol James Troupe In 2005 Spekkens presented a generalization of noncontextuality that applies to imperfect measurements (POVMs) by allowing the underlying hidden variable model to be indeterministic. In addition, unlike traditional Bell-Kochen-Specker noncontextuality, HV models of a single qubit were shown to be \textit{contextual} under this definition. Thus, not all single qubit POVM measurement outcomes can be modeled classically. Recently M. Pusey showed that, under certain conditions, exhibiting an anomalous weak value (i.e. values outside the eigenspectrum of the observable) implies contextuality. We will present a new single qubit prepare and measure QKD protocol that uses observation of anomalous weak values of particular observables to estimate the quantum channel error rate and certify the security of the channel. We also argue that it is the ``degree'' of contextuality of the noisy qubits exiting the channel that fundamentally determine the secure key rate. A benefit of this approach is that the security does not depend on the fair sampling assumption, and so is not compromised by Eve controlling Bob's measurement devices. Thus, it retains much of the benefit of ``Measurement Device Independent'' QKD protocols while only using single photon preparations and measurements. [Preview Abstract] |
Thursday, March 17, 2016 4:54PM - 5:06PM |
V44.00009: Investigation of physical implementation of one-way quantum repeaters with multilevel systems Sreraman Muralidharan, Chang-Ling Zou, Linshu Li, Jianming Wen, Liang Jiang Error correcting codes of multilevel systems have been shown to be resource efficient for the correction of erasure errors. One way quantum repeaters based on multilevel systems offer ultrafast key generation rates, while consuming lower resources than qubit based schemes (arxiv:1504.08054). On the other hand, they are technologically demanding. Here, we identify the key technological requirements needed for the implementation of quantum repeaters with multilevel systems and propose different experimental techniques that can be used to overcome the difficulties. We propose a generalized Duan-Kimble scheme for the generation of error correcting codes of multilevel systems with time-bin qudits. [Preview Abstract] |
Thursday, March 17, 2016 5:06PM - 5:18PM |
V44.00010: Long distance quantum communication using continuous variable encoding Linshu Li, Victor V. Albert, Marios Michael, Sreraman Muralidharan, Changling Zou, Liang Jiang Quantum communication enables faithful quantum state transfer between different parties and protocols for cryptographic purposes. However, quantum communication over long distances (\textgreater 1000km) remains challenging due to optical channel attenuation. This calls for investigation on developing novel encoding schemes that correct photon loss errors efficiently. In this talk, we introduce the generalization of multi-component Schr\"{o}dinger cat states [1] and propose to encode quantum information in these cat states for ultrafast quantum repeaters [2,3]. We detail the quantum error correction procedures at each repeater station and characterize the performance of this novel encoding scheme given practical imperfections, such as coupling loss. A comparison with other quantum error correcting codes for bosonic modes will be discussed. [1] M. Mirrahimi, Z. Leghtas, V. V. Albert, S. Touzard, R. J. Schoelkopf, L. Jiang, and M. H. Devoret, New J. Phys. 16, 045014 (2014). [2] S. Muralidharan, J. Kim, N. L\"{u}tkenhaus, M. D. Lukin, and L. Jiang, Phys. Rev. Lett. 112, 250501 (2014). [3] S. Muralidharan, L. Li, J. Kim, N. L\"{u}tkenhaus, M. D. Lukin, and L. Jiang, arXiv:1509.08435 [Preview Abstract] |
Thursday, March 17, 2016 5:18PM - 5:30PM |
V44.00011: Quantum Secure Direct Communication in a noisy environment: Theory and Experiment Gui Lu Long Quantum communication holds promise for absolutely security in secret message transmission. Quantum secure direct communication (QSDC) is an important branch of the quantum communication in which secret messages are sent directly over a quantum channel with security[Phys. Rev. A 65 , 032302 (2002)]. QSDC offers higher security and is instantaneous in communication, and is a great improvement to the classical communication mode. It is also a powerful basic quantum communication primitive for constructing many other quantum communication tasks such as quantum bidding, quantum signature and quantum dialogue and so on. Since the first QSDC protocol proposed in 2000, it has become one of the extensive research focuses. In this talk, the basic ideas of QSDC will be reviewed, and major QSDC protocols will be described, such as the efficient-QSDC protocol, the two-step QSDC protocol, the one-time-pad QSDC protocol, the high-dimensional QSDC protocol and so on. Experimental progress is also developing steadily, and will also be reviewed. In particular, the quantum one-time-pad QSDC protocol has recently been successfully demonstrated experimentally[arXiv:1503.00451]. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700