Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session U6: Quantum Information and Communication |
Hide Abstracts |
Chair: Hermann Uys, Council for Scientific and Industrial Research, South Africa Room: 302 |
Friday, June 7, 2013 10:30AM - 10:42AM |
U6.00001: Efficient teleportation between remote single-atom quantum memories Stephan Ritter, Christian N\"{o}lleke, Andreas Neuzner, Andreas Reiserer, Carolin Hahn, Gerhard Rempe Teleportation is a prerequisite for the transfer of quantum information over large distances when the losses inherent in any quantum channel preclude a direct transfer. We demonstrate teleportation between two single-atom quantum memories in distant laboratories. By implementing a time-resolved photonic Bell-state measurement (BSM), which is based on two-photon quantum inference, we achieve a teleportation fidelity of $88\,\%$, largely determined by our entanglement fidelity. The problem of limited photon collection efficiency in free space is overcome by trapping each atom in an optical cavity. Compared to previous experiments with remote single material qubits, our approach boosts the overall efficiency by almost five orders of magnitude. This results in success probabilities not predominantly limited by the photon generation and collection efficiency but by the transmission and detection losses inherent in the photonic BSM. [Preview Abstract] |
Friday, June 7, 2013 10:42AM - 10:54AM |
U6.00002: Quantum Random Numbers Guaranteed by Kochen-Specker Theorem Mark Um, Xiang Zhang, Junhua Zhang, Ye Wang, Yang-Chao Shen, Dong-Ling Deng, Lu-Ming Duan, Kihwan Kim We present a random number generator certified by Kochen-Specker (KS) theorem with a trapped ion system. Outcomes of quantum theory are intrinsically random and can be used to produce genuine randomness. In real implementation, however, the true randomness is inevitably mingled with classical noise or control imperfection and cannot be decisively certified. The KS inequality differentiates the results of quantum mechanics from those of classical theory, non-contextual in nature. We demonstrate the experimental violations of the KS inequality, in particular, the Klyachko-Can-Binicioglu-Shumovsky (KCBS) inequality without the detection loophole and reasonably without the compatibility loophole. The violations are used to certify the randomness of a generated string. As a proof of principle, we produce 1 $\times$ 10$^5$ random numbers that contain 5.2 $\times$ 10$^4$ bits of minimum entropy. This work was supported by the National Basic Research Program of China Grant 2011CBA00300, 2011CBA00301, 2011CBA00302, the National Natural Science Foundation of China Grant 61073174, 61033001, 61061130540. KK acknowledges the support of the Thousand Young Talents plan. [Preview Abstract] |
Friday, June 7, 2013 10:54AM - 11:06AM |
U6.00003: Quantum secret sharing with continuous variable cluster states Hoi Kwan Lau, Christian Weedbrook We extend the idea of cluster state quantum secret sharing to the continuous variable regime. Both classical and quantum information can be shared by distributing finitely squeezed continuous variable cluster states through either secure or insecure channels. We show that the security key rate of the classical information sharing can be obtained by standard continuous variable quantum key distribution techniques. We analyse the performance of quantum state sharing by computing the shared entanglement of between the authorised parties and the dealer. Our techniques can be applied to analyse the security of general continuous variable quantum secret sharing. [Preview Abstract] |
Friday, June 7, 2013 11:06AM - 11:18AM |
U6.00004: Information gain in tomography - A quantum signature of chaos Vaibhav Madhok, Carlos Riofrio, Shohini Ghose, Ivan Deutsch We find quantum signatures of classical chaos in various metrics of information gain in quantum tomography. We employ a quantum state estimator based on weak collective measurements of an ensemble of identically prepared systems. The tomographic measurement record consists of a sequence of expectation values of a Hermitian operator that evolves under repeated application of the Floquet map of the quantum kicked top. We find an increase in information gain and hence higher fidelities in the reconstruction algorithm when the chaoticity parameter map increases. The results are well predicted by random matrix theory. [Preview Abstract] |
Friday, June 7, 2013 11:18AM - 11:30AM |
U6.00005: Experimentally efficient methods for estimating the performance of quantum measurements Easwar Magesan, Paola Cappellaro Efficient methods for characterizing the performance of quantum measurements are important in the experimental quantum sciences. Ideally, one requires both a physically relevant distinguishability measure between measurements and a straightforward experimental procedure for estimating the distinguishability measure. We propose the average measurement fidelity and error as distinguishability measures and provide protocols for obtaining bounds on these quantities. The protocols are estimable using experimentally accessible quantities and scalable in the size of the quantum system. We explain why the bounds should be valid in large generality and illustrate the method via numerical examples. [Preview Abstract] |
Friday, June 7, 2013 11:30AM - 11:42AM |
U6.00006: Overheads for the Toric Code in the Presence of Bit or Phase Flip Errors Fern Watson, Tom Stace, Sean Barrett In this talk we will consider one proposal for topological quantum error correction: Kitaev's 2d toric code. The toric code distance scales with lattice size, making a physically larger code more robust. However, a smaller code is desirable because the experimental challenges in creating and manipulating such a state also scale with the number of qubits in the code. The overhead is a balance between these two requirements; in other words the minimum code size that will protect the state with a given accuracy, for a known error rate.~We consider different approaches to revealing the overhead, including both analytic~approximations~and numerically investigations. We find that for a large range of parameter space the overhead for the toric code is polylogarithmic in the desired fidelity. [Preview Abstract] |
Friday, June 7, 2013 11:42AM - 11:54AM |
U6.00007: Quantum Channels that cannot Transmit Quantum Correlations can Generate Quantum Entanglement from Classical Correlation Laszlo Gyongyosi, Sandor Imre One of the most fundamental questions in the development of future communication networks is the process of entanglement transmission. If it were possible to find quantum channels that could generate entanglement between two distant points without sending the entanglement itself over the links, then we could dramatically reduce the cost of development of future quantum communication networks. We prove that the noise transformation of quantum channels that are not able to transmit quantum entanglement can be used to generate entanglement from classically correlated, fully separable unentangled input. We call this new phenomenon the Correlation Conversion property (CC-property) of quantum channels. The proposed solution does not require any local operations or local measurement, only the use of standard quantum channels. Our results have serious implications and fundamental consequences for the future of quantum communications, and for the development of global-scale quantum communication networks. It also makes possible to reduce dramatically the cost of development of global quantum communication networks and quantum repeaters. [Preview Abstract] |
Friday, June 7, 2013 11:54AM - 12:06PM |
U6.00008: On the quantum nonlocality of mode-entangled states capable of sub--shot-noise phase estimation Kaushik Seshadreesan, Hwang Lee, Jonathan Dowling Quantum interferometry has important applications in areas such as precision metrology, sensing, imaging and lithography. Probe states carrying quantum correlations enable estimation of the unknown phase of a two-mode/level interferometer with precisions superior to those achieved by classical probes. Among the different types of quantum correlations, however, quantum entanglement was recently shown to be a necessary resource for achieving sub--shot-noise phase sensitivities. All pure entangled states violate a Bell-type inequality, and thus exhibit quantum nonlocality. In an attempt to uncover the role of quantum nonlocality in the enhancement of phase sensitivity with pure entangled states, we investigate the violation of a hierarchy of Bell-type inequalities for a class of entangled Fock states of fixed photon number $N$, of the form: \begin{equation} |\psi_{m,m'}\rangle=\frac{1}{2}(|m,m'\rangle+e^{i (m-m')\phi}|m',m\rangle),\nonumber \end{equation} where $m\neq m'$, $m+m'=N$, and $m-m'\geq\sqrt{N}$, which include the N00N state, and are capable of sub-shot noise phase estimation in optical interferometry. Our results show interesting trends in the maximum violation of a Bell inequality by the different states of the above type for a fixed total photon number. [Preview Abstract] |
Friday, June 7, 2013 12:06PM - 12:18PM |
U6.00009: Modeling Quantum Noise for efficient testing of fault-tolerant circuits Daniel Puzzuoli, Easwar Magesan, Christopher Granade, David Cory Experimental implementations of quantum logic gates are affected by noise. For simple noise models and encoding schemes, threshold theorems exist which place bounds on the acceptable strength of the noise. In general, finding threshold values for an encoding scheme is a difficult task. Therefore it is desirable to simulate the performance of large encoded circuits to numerically estimate threshold values. For general circuits and noise models, these simulations quickly become intractable in the size of the encoded circuit. We introduce methods for approximating a noise process by one which allows for efficient Monte Carlo simulation of properties of encoded circuits [1]. The approximations are as close to the original process as possible without overestimating their ability to preserve quantum information, a key property for obtaining more honest estimates of threshold values.\\[4pt] [1] Phys. Rev. A 87, 012324 (2013). [Preview Abstract] |
Friday, June 7, 2013 12:18PM - 12:30PM |
U6.00010: The quantum computer game: citizen science Sidse Damgaard, Klaus M{\O}lmer, Jacob F. Sherson Progress in the field of quantum computation is hampered by daunting technical challenges. Here we present an alternative approach to solving these by enlisting the aid of computer players around the world. We have previously examined a quantum computation architecture involving ultracold atoms in optical lattices and strongly focused tweezers of light [1]. In The Quantum Computer Game (see http://www.scienceathome.org/), we have encapsulated the time-dependent Schr\"{o}dinger equation for the problem in a graphical user interface allowing for easy user input. Players can then search the parameter space with real-time graphical feedback in a game context with a global high-score that rewards short gate times and robustness to experimental errors. The game which is still in a demo version has so far been tried by several hundred players. Extensions of the approach to other models such as Gross-Pitaevskii and Bose-Hubbard are currently under development. The game has also been incorporated into science education at high-school and university level as an alternative method for teaching quantum mechanics. Initial quantitative evaluation results are very positive.\\[4pt] [1] C. Weitenberg et al, Phys. Rev. A, 84, 032322 (2011) [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