Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session P6: Entanglement and Error Correction |
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Chair: Nicholas Guise, NIST Room: Garden 4 |
Thursday, June 7, 2012 2:00PM - 2:12PM |
P6.00001: Quantum Entanglement in Spinor Bose-Einstein Condensates and the Preparation of Dicke State Zhen Zhang, Luming Duan The spin-1 Bose Einstein Condensate system can exhibit many interesting phenomena under the effect of linear and quadratic Zeeman effects, resulting from the rich spin texture and the long range correlation in the system. The manybody ground state is shown and phase transition and entanglement properties are discribed. We also propose a method to prepare the Dicke state, with time evolution from a state relatively easy to realise from current experimental cooling methods. The entanglement depth, which based only on the measuring of collective spin operators, is used to characterise the entanglement in the final prepared state. Various noises in the preparation process are also discussed. [Preview Abstract] |
Thursday, June 7, 2012 2:12PM - 2:24PM |
P6.00002: Correcting detection error in quantum computation and state engineering through data processing Chao Shen, Luming Duan Quantum error correction in general is experimentally challenging as it requires significant expansion of the size of quantum circuits and accurate performance of quantum gates to fulfill the error threshold requirement. Here we propose a method much simpler for experimental implementation to correct arbitrary detection errors. The method is based on processing of data from repetitive experiments and can correct detection error of any magnitude, as long as the error magnitude is calibrated. The method is illustrated with its application to detection of multi-partite entanglement from quantum state engineering. [Preview Abstract] |
Thursday, June 7, 2012 2:24PM - 2:36PM |
P6.00003: Experimental demonstration of quantum gain in a zero-sum game Chong Zu, Yuexuan Wang, Xiuying Chang, Zhaohui Wei, Shengyu Zhang, Luming Duan We propose and experimentally demonstrate a zero-sum game which is in a fair Nash equilibrium for classical players, but a quantum player can always win using an appropriate strategy. The gain of the quantum player is measured experimentally under different quantum strategies and input states. It is found that the quantum gain is maximized under a maximally entangled state, but does not reduce to zero when entanglement disappears. Instead, it links with another kind of quantum correlation described by discord for the qubit case. [Preview Abstract] |
Thursday, June 7, 2012 2:36PM - 2:48PM |
P6.00004: Experimental demonstration of topological error correction Xing-Can Yao, Wei-Bo Gao, You-Jin Deng, Yu-Ao Chen, Jian-Wei Pan, Austin Fowler, Robert Raussendorf Scalable quantum computing can only be achieved if qubits are manipulated fault-tolerantly. Topological error correction---a novel method which combines topological quantum computing and quantum error correction---possesses the highest known tolerable error rate for a local architecture. This scheme makes use of cluster states with topological properties and requires only nearest-neighbor interactions. Here we report the first experimental demonstration of topological error correction with an eight-photon cluster state. It is shown that a correlation can be protected against a single error on any qubit, and when all qubits are simultaneously subjected to errors with equal probability, the effective error rate can be significantly reduced. This demonstrates the viability of topological error correction. Our work represents the first experimental effort to achieve fault-tolerant quantum information processing by exploring the topological properties of quantum states. [Preview Abstract] |
Thursday, June 7, 2012 2:48PM - 3:00PM |
P6.00005: Accessible non-linear witnesses Norbert L{\"u}tkenhaus, Oleg Gittsovich, Juan Miguel Arrazola Verification of entanglement is an important tool to characterize sources and devices for use in quantum computing and communication applications. Evaluation of entanglement witnesses are an especially valuable tool, especially for higher-dimensional systems, as they do not require a full reconstruction of the underlying quantum state (tomography). Linear witnesses can be extended to series of non-linear witnesses [1, 2] so that each element of this family detects a strictly larger set of entangled states than the previous one. In our contribution we show that one can construct series of {\em accessible} non-linear witnesses that can be evaluated using exactly the same data as for the evaluation of the original linear witness. This allows a reanalysis of published experimental data to strengthen statements about entanglement verification without the requirement to perform additional measurements. Accessible non-linear witnesses allow the verification of entanglement without critical dependence on having found the ``right'' linear witness. They can also enhance the statistical significance of the entanglement verification. \\[4pt] [1] O. G{\"u}hne and N. L{\"u}tkenhaus, PRL 96, 170502 (2006)\\[0pt] [2] T. Moroder, O. G{\"u}hne, and N. L{\"u}tkenhaus, PRA 78, 032326 (2008) [Preview Abstract] |
Thursday, June 7, 2012 3:00PM - 3:12PM |
P6.00006: Improved data analysis for verifying quantum nonlocality and entanglement Yanbao Zhang, Scott Glancy, Emanuel Knill Given a finite number of experimental results originating from local measurements on two separated quantum systems in an unknown state, are these systems nonlocally correlated or entangled with each other? These properties can be verified by violating a Bell inequality or satisfying an entanglement witness. However, violation or satisfaction could be due to statistical fluctuations in finite measurements. Rigorous upper bounds, on the maximum probability (i.e., the p-value) according to local realistic or separable states of a violation or satisfaction as high as the observed, are required. Here, we propose a rigorous upper bound that improves the known bound from large deviation theory [R. Gill, arXiv:quant-ph/0110137]. The proposed bound is robust against experimental instability and the memory loophole [J. Barrett et al., Phys. Rev. A 66, 042111 (2002)]. Compared with our previous method [Phys. Rev. A 84, 062118 (2011)], the proposed method takes advantage of the particular Bell inequality or entanglement witness tested in an experiment, so the computation complexity is reduced. Also, this method can be easily extended to test a set of independent Bell inequalities or entanglement witnesses simultaneously. [Preview Abstract] |
Thursday, June 7, 2012 3:12PM - 3:24PM |
P6.00007: Evaluation of joint probabilities for non-commuting observables from correlations between quantum clones Holger Hofmann Universal quantum cloning processes must be able to copy all physical properties of a quantum system with equal fidelity. If the statistical interpretation of the quantum state is correct, quantum fluctuations of the input state are also copied, mapping the correlations between non-commuting observables onto the experimentally accessible correlations between separate systems. Here, I show that it is indeed possible to evaluate the correlations between the non-commuting properties of a quantum system from the correlations between measurements of two optimal quantum clones of the system. Significantly, the joint probabilities obtained from the analysis of cloning correlations are identical with the joint probabilities observed in weak measurements, indicating that such joint probabilities may provide the foundations for a consistent statistical interpretation of quantum physics. [Preview Abstract] |
Thursday, June 7, 2012 3:24PM - 3:36PM |
P6.00008: Quantum Polar Coding for Noisy Optical Quantum Channels Laszlo Gyongyosi, Sandor Imre Polar channel coding is a revolutionary encoding and decoding scheme, which makes possible the construction of codewords to achieve the symmetric capacity of noisy communication channels. Here, we show that by using quantum polar codes, the symmetric classical capacity of noisy optical quantum channels can be achieved. We also demonstrate the existence of quantum polar codes capable of transmitting classical information privately, although initially theses channels had zero private classical capacity. As we prove, there also exist polar coding-based codewords for the transmission of quantum entanglement; however, these channels are so noisy that they cannot transmit any quantum information. [Preview Abstract] |
Thursday, June 7, 2012 3:36PM - 3:48PM |
P6.00009: An ab-initio model of anomalous heating in planar ion traps Arghavan Safavi-Naini, Peter Rabl, Philippe Weck, Hossein Sadeghpour Anomalous heating of trapped ions imposes a limit on the scalability of the planar trap architecture for quantum computation. Measurements of the electric field noise present in ion traps have determined the frequency scaling of this noise and its scaling with the distance from the ion to the trap surface [1,2]. These measurements suggest that a thermally activated random process is at work. We present a model that accounts for the noise due to oscillating dipoles on the trap electrode surface [3]. The dipoles are formed when atoms are adsorbed on the trap surface. We present calculations for the spectral noise density and its distance and frequency scaling. We go beyond independent dipoles and consider the effect of correlation between dipoles, presence of a monolayer on the trap surface and multi-phonon processes on the spectral density. \\[4pt] [1] Q. A. Turchette et. al., Phys. Rev. A. 61, 63418 (2000).\\[4pt] [2] D. A. Hite et. al., arXiv:1112.5419v1.\\[0pt] [3] A. Safavi-Naini, P. Rabl, P. F. Weck, H. R. Sadeghpour, Phys. Rev. A. 84, 023412 (2011). [Preview Abstract] |
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