- Kwek, Leong Chuan

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# Kwek, Leong Chuan

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Kwek, Leong Chuan

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leongchuan.kwek@nie.edu.sg

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Natural Sciences & Science Education (NSSE)

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7006483792

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- PublicationOpen AccessRepeat-until-success distributed quantum computation by using single-photon interference at a beam splitter
Show more A repeat-until-success (RUS) measurement-based scheme for the implementation of the distributed quantum computation by using single-photon interference at a 50:50 beam splitter is proposed. It is shown that the 50:50 beam splitter can naturally project a suitably encoded matter-photon state to either a desired entangling gate-operated state of the matter qubits or to their initial state when the photon is detected. The recurrence of the initial state permits us to implement the desired entangling gate in a RUS way. To implement a distributed quantum computation we suggest an encoding method by means of the effect of dipole-induced transparency proposed recently [E. Waks and J. Vuckovic, Phys. Rev. Lett. 96, 153601 (2006)]. The effects of the unfavorable factors on our scheme are also discussed.Show more WOS© Citations 4Scopus© Citations 4 150 172 - PublicationOpen AccessMultiparticle entanglement resolution analyzer based on quantum-control-assisted uncertainty relation(Wiley, 2021)
;Ma, Shao-Qiang ;Zheng, Xiao ;Zhang, Guo-Feng ;Fan, Heng ;Liu, Wu-MingShow more We construct a quantum-control-assisted multi-observable variance-based uncertainty relation, and the uncertainty relation obtained indicates that we can prepare a quantum state, in which the measurement results of any observables can be predicted precisely with the help of quantum control and entanglement resource. The new variance-based uncertainty relation provides a concept of "multiparticle entanglement resolution lines" for multiparticle entangled pure states, that can delineate different multiparticle entanglement classes, and thus it can be considered as an analyzer of multiparticle entanglement classes. The analyzer is used to identify different multiparticle entanglement classes with a suitable number of incompatible measurements, without a complete knowledge of the quantum state.Show more WOS© Citations 2Scopus© Citations 2 264 110 - PublicationOpen AccessIncorporating nature of science elements in A-level physics lessons in Singapore.(National Institute of Education (Singapore), 2020)
;Subramaniam, R. (Ramanathan) ;Wong, Choun Pei ;Wee, Andrew; ;Sow, Chorng Haur ;Chew, CharlesWong, DarrenShow more 196 160 - PublicationMetadata onlyGraph-theoretic approach for self-testing in Bell scenarios(American Physical Society, 2022)
;Kishor Bharti ;Ray, Maharshi ;Xu, Zhen-Peng ;Hayashi, Masahito; Cabello, AdanShow more Self-testing is a technology to certify states and measurements using only the statistics of the experiment. Self-testing is possible if some extremal points in the set B_{Q}of quantum correlations for a Bell experiment are achieved, up to isometries, with specific states and measurements. However, B_{Q}is difficult to characterize, so it is also difficult to prove whether or not a given matrix of quantum correlations allows for self-testing. Here, we show how some tools from graph theory can help to address this problem. We observe that B_{Q}is strictly contained in an easy-to-characterize set associated with a graph, Θ(G). Therefore, whenever the optimum over B_{Q}and the optimum over Θ(G)) coincide, self-testing can be demonstrated by simply proving self-testability with Θ(G). Interestingly, these maxima coincide for the quantum correlations that maximally violate many families of Bell-like inequalities. Therefore, we can apply this approach to prove the self-testability of many quantum correlations, including some that are not previously known to allow for self-testing. In addition, this approach connects self-testing to some open problems in discrete mathematics. We use this connection to prove a conjecture [M. Araujo et a/., Phys. Rev. A, 88, 022118 (2013)] about the closed-form expression of the Lovasz theta number for a family of graphs called the Mobius ladders. Although there are a few remaining issues (e.g., in some cases, the proof requires the assumption that measurements are of rank 1). this approach provides an alternative method to self-testing and draws interesting connections between quantum mechanics and discrete mathematics.Show more WOS© Citations 2 55 - PublicationMetadata onlyIntegrated photonic computing chip for unary-based option pricing(Optica Publishing Group, 2024)
;Zhang, Hui ;Ramos-Calderer, Sergi ;Zhan, Yuancheng ;Cai, Hong ;Lo, Guo-Qiang; ;Latorre, José IgnacioLiu, Ai QunShow more A specialized photonic chip is demonstrated for unary European option pricing and quantum amplitude estimation is adopted to overcome classical computing bottlenecks. The chip achieves precise asset distribution modeling and prediction, significantly enhancing financial industry eﬃciency and services.Show more 21 - PublicationMetadata onlyQuantum computers: Theory and algorithms
Show more Highlights the advantages of a quantum over a classical computer. Reviews the concepts of the classical and quantum computers along with circuits and gates. Uses the Deutsch, Grover, and Shor algorithms for highlighting key features of quantum computingShow more Scopus© Citations 6 36 - PublicationOpen AccessStatistical reconstruction of qutrits(American Physical Society, 2004)
;Bogdanov, Yu. I. ;Chekhova, M. V. ;Krivitsky, L. A. ;Kulik, S. P. ;Penin, A. N. ;Zhukov, A. A.; ;Oh, Choo HiapTey, M. K.Show more We discuss a procedure of measurement followed by the reproduction of the quantum state of a three-level optical system—a frequency—and spatially degenerate two-photon field. The method of statistical estimation of the quantum state based on solving the likelihood equation and analyzing the statistical properties of the obtained estimates is developed. Using the root approach of estimating quantum states, the initial two-photon state vector is reproduced from the measured fourth moments in the field. The developed approach applied to quantum-state reconstruction is based on the amplitudes of mutually complementary processes. The classical algorithm of statistical estimation based on the Fisher information matrix is generalized to the case of quantum systems obeying Bohr’s complementarity principle. It has been experimentally proved that biphoton-qutrit states can be reconstructed with the fidelity of 0.995–0.999 and higher.Show more WOS© Citations 65Scopus© Citations 77 333 253 - PublicationOpen AccessFisher information as general metrics of quantum synchronization
Show more Quantum synchronization has emerged as a crucial phenomenon in quantum nonlinear dynamics with potential applications in quantum information processing. Multiple measures for quantifying quantum synchronization exist. However, there is currently no widely agreed metric that is universally adopted. In this paper, we propose using classical and quantum Fisher information (FI) as alternative metrics to detect and measure quantum synchronization. We establish the connection between FI and quantum synchronization, demonstrating that both classical and quantum FI can be deployed as more general indicators of quantum phase synchronization in some regimes where all other existing measures fail to provide reliable results. We show advantages in FI-based measures, especially in 2-to-1 synchronization. Furthermore, we analyze the impact of noise on the synchronization measures, revealing the robustness and susceptibility of each method in the presence of dissipation and decoherence. Our results open up new avenues for understanding and exploiting quantum synchronization.Show more 39 66 - PublicationOpen AccessBeating the Clauser-Horne-Shimony-Holt and the Svetlichny games with optimal states(American Physical Society, 2016)
;Su, Hong-Yi ;Ren, Changliang ;Chen, Jing-Ling ;Zhang, Fu-Ling ;Wu, Chunfeng ;Xu, Zhen-Peng ;Gu, Mile ;Sai VinjanampathyShow more We study the relation between the maximal violation of Svetlichny’s inequality and the mixedness of quantum states and obtain the optimal state (i.e., maximally nonlocal mixed states, or MNMS, for each value of linear entropy) to beat the Clauser-Horne-Shimony-Holt and the Svetlichny games. For the two-qubit and three-qubit MNMS, we showed that these states are also the most tolerant state against white noise, and thus serve as valuable quantum resources for such games. In particular, the quantum prediction of the MNMS decreases as the linear entropy increases, and then ceases to be nonlocal when the linear entropy reaches the critical points 2/3 and 9/14 for the two- and three-qubit cases, respectively. The MNMS are related to classical errors in experimental preparation of maximally entangled states.Show more WOS© Citations 3Scopus© Citations 3 318 149 - PublicationOpen AccessGeneralized flying-qudit scheme in arbitrary dimensions
Show more We generalize in higher dimensions the so-called “flying-qubit scheme” that was described in the paper by Lim, Beige, and Kwek Phys. Rev. Lett. 95, 030505 2005 . In that paper, the authors proposed a scheme according to which distant atoms get entangled during a measurement, in the Bell basis, of photons flying qubits emitted by them. We show that although in principle a generalization of this scheme to arbitrary dimensions is possible, this theoretical proposal is not presently feasible in all dimensions because only qubit Bell states have been successively measured until now. Nevertheless we show that a many-qubits generalization of the flying-qubit scheme factorizes and reduces to the realization, in parallel, of many individual single-qubit schemes, for which it is known that they are realizable experimentally with the techniques that are available today. In other words, our approach shows that when d is an even prime power d=2m , the flyingqudit scheme reduces to m flying-qubit schemes. For d=2m and arbitrary m the implementation of a generalized, maximally entangling, conditional qudit phase gate “with insurance” or “repeat-until-success” is thus shown to be feasible in practice by coupling m pairs of two-level atoms to m pairs of two-level polarized photons. Moreover, due to the parallelism of the task, the time necessary for completing successfully the task scales logarithmically in a function of m while at the same time the dimension of the Hilbert space scales exponentially which presents promising perspectives regarding quantum informational realizations such as the quantum computer.Show more WOS© Citations 3Scopus© Citations 3 127 182