ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 25 Aug 2019 09:27:50 GMT2019-08-25T09:27:50Z50221- Hyperfine interaction induced decoherence and quantum information processing with quantum dotshttps://scholarbank.nus.edu.sg/handle/10635/98744Title: Hyperfine interaction induced decoherence and quantum information processing with quantum dots
Authors: Zhu, Y.; Yu, S.; Yeo, Y.
Abstract: Employing a realistic model of the nuclear spin bath, we derive exact dynamical mappings that describe the basic operations in quantum information processing with electron spin qubits in quantum dots. © 2008 Optical Society of America.
Tue, 01 Jan 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/987442008-01-01T00:00:00Z
- The world in slow motion: Using a high-speed camera in a physics workshophttps://scholarbank.nus.edu.sg/handle/10635/98329Title: The world in slow motion: Using a high-speed camera in a physics workshop
Authors: Dewanto, A.; Lim, G.Q.; Kuang, J.; Zhang, J.; Yeo, Y.
Abstract: We present a physics workshop for college students to investigate various physical phenomena using high-speed cameras. The technical specifications required, the step-by-step instructions, as well as the practical limitations of the workshop, are discussed. This workshop is also intended to be a novel way to promote physics to Generation-Y learners who are attuned to a more visually engaging teaching style. © 2012 IOP Publishing Ltd.
Thu, 01 Nov 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/983292012-11-01T00:00:00Z
- Three-qubit thermal entanglement via entanglement swapping on two-qubit Heisenberg XY chainshttps://scholarbank.nus.edu.sg/handle/10635/98404Title: Three-qubit thermal entanglement via entanglement swapping on two-qubit Heisenberg XY chains
Authors: Kao, Z.C.; Ng, J.; Yeo, Y.
Abstract: In this paper, we consider the generation of a three-qubit Greenberger-Horne-Zeilinger-like thermal state by applying the entanglement swapping scheme of Zukowski [Ann. N. Y. Acad. Sci. 755, 91 (1995)] to three pairs of two-qubit Heisenberg XY chains. The quality of the resulting three-qubit entanglement is studied by analyzing the teleportation fidelity, when it is used as a resource in the teleportation protocol of Karlsson [Phys. Rev. A 58, 4394 (1998)]. We show that even though thermal noise in the original two-qubit states is amplified by the entanglement swapping process, we are still able to achieve nonclassical fidelities for the anisotropic Heisenberg XY chains at finitely higher and higher temperatures by adjusting the strengths of an external magnetic field. This has a positive implication on the solid-state realization of a quantum computer. © 2005 The American Physical Society.
Thu, 01 Dec 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/984042005-12-01T00:00:00Z
- Robustness of multipartite entanglement under collisional decoherencehttps://scholarbank.nus.edu.sg/handle/10635/97830Title: Robustness of multipartite entanglement under collisional decoherence
Authors: Yeo, Y.
Abstract: The collision model of Ziman et al. was considered and the robustness of N-qubit Greenberger-Horne-Zeilinger (GHZ), W, and linear cluster states were studied. Our results show that N-qubit entanglement of GHZ states would be extremely fragile under collisional decoherence, and that of W states could be more robust than of linear cluster states. © 2007 Pleiades Publishing, Ltd.
Wed, 01 Aug 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/978302007-08-01T00:00:00Z
- Quantum nonlocality of four-qubit entangled stateshttps://scholarbank.nus.edu.sg/handle/10635/97696Title: Quantum nonlocality of four-qubit entangled states
Authors: Wu, C.; Yeo, Y.; Kwek, L.C.; Oh, C.H.
Abstract: We derive a Bell inequality for testing violation of local realism. Quantum nonlocality of several four-qubit states is investigated. These include the Greenberger-Zeilinger-Horne (GHZ) state, W state, linear cluster state, and the state | χ that has recently been proposed in. The Bell inequality is optimally violated by | χ but not violated by the GHZ state. The linear cluster state also violates the Bell inequality though not optimally. The state | χ can thus be discriminated from the linear cluster state by using the inequality. Different aspects of four-partite entanglement are also studied by considering the usefulness of a family of four-qubit mixed states as resources for two-qubit teleportation. Our results generalize those in. © 2007 The American Physical Society.
Mon, 26 Mar 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/976962007-03-26T00:00:00Z
- Teleportation and dense coding with genuine multipartite entanglementhttps://scholarbank.nus.edu.sg/handle/10635/98214Title: Teleportation and dense coding with genuine multipartite entanglement
Authors: Yeo, Y.; Chua, W.K.
Abstract: We present an explicit protocol E0 for faithfully teleporting an arbitrary two-qubit state via a genuine four-qubit entangled state. By construction, our four-partite state is not reducible to a pair of Bell states. Its properties are compared and contrasted with those of the four-party Greenberger-Horne- Zeilinger and W states. We also give a dense coding scheme D0 involving our state as a shared resource of entanglement. Both D0 and E0 indicate that our four-qubit state is a likely candidate for the genuine four-partite analogue to a Bell state. © 2006 The American Physical Society.
Sun, 01 Jan 2006 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/982142006-01-01T00:00:00Z
- Teleportation with a mixed state of four qubits and the generalized singlet fractionhttps://scholarbank.nus.edu.sg/handle/10635/98217Title: Teleportation with a mixed state of four qubits and the generalized singlet fraction
Authors: Yeo, Y.
Abstract: Recently, an explicit protocol E0 for faithfully teleporting arbitrary two-qubit states using genuine four-qubit entangled states was presented by us. Here, we show that E0 with an arbitrary four-qubit mixed-state resource Ξ is equivalent to a generalized depolarizing bichannel with probabilities given by the maximally entangled components of the resource. These are defined in terms of our four-qubit entangled states. We define the generalized singlet fraction G [Ξ] and illustrate its physical significance with several examples. We argue that in order to teleport arbitrary two-qubit states with average fidelity better than is classically possible, we have to demand that G [Ξ] > 2. In addition, we conjecture that when G [Ξ] < 4, then no entanglement could be teleported. It is shown that to determine the usefulness of Ξ for E0, it is necessary to analyze G [Ξ]. © 2006 The American Physical Society.
Sun, 01 Jan 2006 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/982172006-01-01T00:00:00Z
- Buzek-Hillery cloning revisited using the Bures metric and trace normhttps://scholarbank.nus.edu.sg/handle/10635/95911Title: Buzek-Hillery cloning revisited using the Bures metric and trace norm
Authors: Kwek, L.C.; Oh, C.H.; Wang, X.-B.; Yeo, Y.
Abstract: The trace norm and Bures metric were used to clone imperfectly arbitrary states. The cloning will be done in a universal cloning machine. The Bures metrics were found to be better way of distinguishing mixed states and quantifying distance between different states in information theory.
Wed, 01 Nov 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/959112000-11-01T00:00:00Z
- Effects of quantum noises and noisy quantum operations on entanglement and special dense codinghttps://scholarbank.nus.edu.sg/handle/10635/96377Title: Effects of quantum noises and noisy quantum operations on entanglement and special dense coding
Authors: Quek, S.; Li, Z.; Yeo, Y.
Abstract: We show how noncommuting noises could cause a Bell state χ0 to suffer entanglement sudden death (ESD). ESD may similarly occur when a noisy operation acts, if the corresponding Hamiltonian and Lindblad operator do not commute. We study the implications of these in special dense coding S. When noises that cause ESD act, we show that χ0 may lose its capacity for S before ESD occurs. Similarly, χ0 may fail to yield information transfer better than classically possible when the encoding operations are noisy, though entanglement is not destroyed in the process. © 2010 The American Physical Society.
Fri, 12 Feb 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/963772010-02-12T00:00:00Z
- Quantum teleportation via a two-qubit Heisenberg XY chain - Effects of anisotropy and magnetic fieldhttps://scholarbank.nus.edu.sg/handle/10635/97708Title: Quantum teleportation via a two-qubit Heisenberg XY chain - Effects of anisotropy and magnetic field
Authors: Yeo, Y.; Liu, T.; Lu, Y.-E.; Yang, Q.-Z.
Abstract: In this paper we study the influence of anisotropy on the usefulness of the entanglement in a two-qubit Heisenberg XY chain at thermal equilibrium in the presence of an external magnetic field, as a resource for quantum teleportation via the standard teleportation protocol. We show that the nonzero thermal entanglement produced by adjusting the external magnetic field beyond some critical strength is a useful resource. We also consider entanglement teleportation via two two-qubit Heisenberg XY chains. © 2005 IOP Publishing Ltd.
Fri, 08 Apr 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/977082005-04-08T00:00:00Z
- Detection of gravitational waves - An application of relativistic quantum information theoryhttps://scholarbank.nus.edu.sg/handle/10635/96188Title: Detection of gravitational waves - An application of relativistic quantum information theory
Authors: Yeo, Y.; Lim, Z.H.; Ching, C.L.; Chong, J.; Chua, W.K.; Dewanto, A.
Abstract: We show that a passing gravitational wave may influence the spin entropy and spin negativity of a system of N massive spin-(1/2) particles, in a way that is characteristic of the radiation. We establish the specific conditions under which this effect may be nonzero. The change in spin entropy and negativity, however, is extremely small. Here, we propose and show that this effect may be amplified through entanglement swapping. Relativistic quantum information theory may have a contribution towards the detection of gravitational waves. Copyright © EPLA, 2007.
Sun, 01 Apr 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/961882007-04-01T00:00:00Z
- Non-Markovian effects on quantum-communication protocolshttps://scholarbank.nus.edu.sg/handle/10635/97356Title: Non-Markovian effects on quantum-communication protocols
Authors: Yeo, Y.; An, J.-H.; Oh, C.H.
Abstract: We show how, under the influence of non-Markovian environments, two different maximally entangled Bell states give rise to states that have equal classical correlations and the same capacities to violate the Bell-Clauser-Horne-Shimony-Holt inequality, but intriguingly differing usefulness for teleportation and dense coding. We elucidate how different entanglement measures like negativity and concurrence, and two different measures of quantum discord, could account for these behaviors. In particular, we explicitly show how the Ollivier-Zurek measure of discord directly accounts for one state being a better resource for dense coding compared to another. Our study leads to several important issues about these measures of discord. © 2010 The American Physical Society.
Thu, 30 Sep 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/973562010-09-30T00:00:00Z
- Entanglement oscillation and survival induced by non-Markovian decoherence dynamics of the entangled squeezed statehttps://scholarbank.nus.edu.sg/handle/10635/96491Title: Entanglement oscillation and survival induced by non-Markovian decoherence dynamics of the entangled squeezed state
Authors: An, J.-H.; Yeo, Y.; Zhang, W.-M.; Oh, C.H.
Abstract: We study the exact decoherence dynamics of the entangled squeezed state of two single-mode optical fields interacting with two independent and uncorrelated environments. We analyze in detail the non-Markovian effects on the entanglement evolution of the initially entangled squeezed state for different environmental correlation time scales. We find that the environments have dual actions on the system: backaction and dissipation. In particular, when the environmental correlation time scale is comparable to the time scale for significant change in the system, the backaction would counteract the dissipative effect. Interestingly, this results in the survival of some residual entanglement in the final steady state. © 2009 IOP Publishing Ltd.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/964912009-01-01T00:00:00Z
- Exact decoherence dynamics of a single-mode optical fieldhttps://scholarbank.nus.edu.sg/handle/10635/96538Title: Exact decoherence dynamics of a single-mode optical field
Authors: An, J.-H.; Yeo, Y.; Oh, C.H.
Abstract: We apply the influence-functional method of Feynman and Vernon to the study of a single-mode optical field that interacts with an environment at zero temperature. Using the coherent-state formalism of the path integral, we derive a generalized master equation for the single-mode optical field. Our analysis explicitly shows how non-Markovian effects manifest in the exact decoherence dynamics for different environmental correlation time scales. Remarkably, when these are equal to or greater than the time scale for significant change in the system, the interplay between the backaction-induced coherent oscillation and the dissipative effect of the environment causes the non-Markovian effect to have a significant impact not only on the short-time behavior but also on the long-time steady-state behavior of the system. © 2009 Elsevier Inc. All rights reserved.
Sat, 01 Aug 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/965382009-08-01T00:00:00Z
- Devastating effects of quantum noises and noisy quantum operations on entanglement and quantum information protocolshttps://scholarbank.nus.edu.sg/handle/10635/98666Title: Devastating effects of quantum noises and noisy quantum operations on entanglement and quantum information protocols
Authors: Yeo, Y.
Abstract: We show that besides noncommuting Lindblad operators, a Hamiltonian together with a noncommuting Lindblad operator produces a noisy operation that could totally destroy the entanglement of a Bell state in a finite time-entanglement sudden death (ESD). Furthermore, we show that these could result in states that become useless for special dense coding and standard teleportation before ESD occurs. We discuss the implications of our results and point out a possible solution to the potential problems. © 2011 American Institute of Physics.
Sat, 01 Jan 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/986662011-01-01T00:00:00Z
- Effects of Pauli channels and noisy quantum operations on standard teleportationhttps://scholarbank.nus.edu.sg/handle/10635/96373Title: Effects of Pauli channels and noisy quantum operations on standard teleportation
Authors: Yeo, Y.; Kho, Z.-W.; Wang, L.
Abstract: Quantum noises generated by non-commuting Pauli operators may also cause entanglement sudden death (ESD). In this work, stimulated by this observation, we show how a Pauli-X or -Y gate could also destroy entanglement in a finite time when they are executed in the presence of dephasing noise. Motivated by the fact that they are basic to quantum information processing, we analyze the impact of noisy operations and non-commuting noises on single- and two-qubit teleportation - archetype of quantum communication. By considering the decoherence dynamics during establishment of the channel states and noisy recovery operations, we show that there is a finite lifetime for a standard teleportation to be completed before it loses the quantum advantage over purely classical communication. © EPLA, 2009.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/963732009-01-01T00:00:00Z
- Hyperfine-interaction-induced decoherence and deterministic teleportation of electrons in a quantum-dot nanostructurehttps://scholarbank.nus.edu.sg/handle/10635/96856Title: Hyperfine-interaction-induced decoherence and deterministic teleportation of electrons in a quantum-dot nanostructure
Authors: Yu, S.; Zhu, Y.; Yeo, Y.
Abstract: Recently, de Visser and Blaauboer [Phys. Rev. Lett. 96, 246801 (2006)] proposed the most efficient deterministic teleportation protocol T for electron spins in a semiconductor nanostructure consisting of a single and a double quantum dot. However, it is as yet unknown if T can be completed before decoherence sets in. In this paper we analyze the detrimental effect of nuclear spin baths, the main source of decoherence, on T. We show that nonclassical teleportation fidelity can be achieved with T provided certain conditions are met. Our study indicates that realization of quantum computation with quantum dots is indeed promising. © 2008 The American Physical Society.
Fri, 27 Jun 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/968562008-06-27T00:00:00Z
- Entanglement of three qubitshttps://scholarbank.nus.edu.sg/handle/10635/96490Title: Entanglement of three qubits
Authors: Wu, C.; Chen, J.-L.; Kwek, L.C.; Yeo, Y.; Oh, C.H.
Abstract: For the formulation of Bell inequalities, it is important to include not just N-site correlation functions, but also (N-n)-site correlation functions. In this article, we focus on a three-qubit Bell inequality, which has been shown to be a good candidate for generalizing Gisin's theorem to three qubits. The three-qubit Bell inequality can be used to detect the W-type entanglement in a proposed experiment. © 2007 MAIK "Nauka/Interperiodica".
Wed, 01 Aug 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/964902007-08-01T00:00:00Z
- Local noise can enhance two-qubit teleportationhttps://scholarbank.nus.edu.sg/handle/10635/97083Title: Local noise can enhance two-qubit teleportation
Authors: Yeo, Y.
Abstract: For single-qubit teleportation, it has been shown that there is a family of two-qubit mixed states whose teleportation fidelity can be enhanced by subjecting one of the qubits to an amplitude damping channel. This is an interesting result, since noise in general degrades quantum entanglement. It is believed that this enhancement is due to an improvement in the classical correlations of the two-qubit states. Here, we consider two-qubit teleportation using a family of four-qubit mixed states as a resource. In this context, we show that one can again achieve enhancement in teleportation fidelity via dissipative interactions with the local environment. For a rather general class of input states, we find that this improvement implies an enhancement in the quantum discord of some teleported states. We conjecture that an improvement in some quantum property of the four-qubit mixed states could have resulted from the local interactions. We expect that our analysis will make an important case study for future investigations on the different aspects of composite quantum systems. © 2008 The American Physical Society.
Mon, 25 Aug 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/970832008-08-25T00:00:00Z
- Robust multipartite thermal entanglementhttps://scholarbank.nus.edu.sg/handle/10635/115274Title: Robust multipartite thermal entanglement
Authors: Kwong, C.C.; Yeo, Y.
Abstract: Recently, Mintert et al (MKB) (2005 Phys. Rev. Lett. 95 260502) proposed generalizations of the Wootters concurrence for multipartite quantum systems, which can be evaluated efficiently for arbitrary mixed states. In this paper, we study in detail the origin of the robustness of multipartite thermal entanglement in N-qubit XY models with N = 2, 4 and 6 using the MKB concurrences. For N = 2, we establish the principle for the occurrence of robust bipartite thermal entanglement (Kamta and Starace 2002 Phys. Rev. Lett. 88 107901). We show explicitly that similar robust multipartite thermal entanglement can be found in the N = 4 case, and how this can be explained employing the same principle. It is then deduced that the six-qubit XY model also possesses robust multipartite thermal entanglement like the N = 2 case. More generally, our work spells out the characteristic properties for a given realistic model to have robust multipartite thermal entanglement like that in the two-qubit XY model. © 2008 IOP Publishing Ltd.
Fri, 25 Jul 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1152742008-07-25T00:00:00Z
- Effects of collisional decoherence on multipartite entanglement: How entanglement might not be relatively commonhttps://scholarbank.nus.edu.sg/handle/10635/96358Title: Effects of collisional decoherence on multipartite entanglement: How entanglement might not be relatively common
Authors: Low, G.-H.; Shi, Z.; Yeo, Y.
Abstract: We consider the collision model of Ziman and study the robustness of N -qubit Greenberger-Horne-Zeilinger (GHZ), W, and linear cluster states. Our results show that N -qubit entanglement of GHZ states would be extremely fragile under collisional decoherence, and that of W states could be more robust than that of linear cluster states. We indicate that the collision model of Ziman could provide a physical mechanism for some known results in this area of investigation. More importantly, we show that it could give a clue as to how N -partite distillable entanglement would be relatively rare in our macroscopic classical world. © 2006 The American Physical Society.
Sun, 01 Jan 2006 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/963582006-01-01T00:00:00Z
- Non-Markovian environments and entanglement preservationhttps://scholarbank.nus.edu.sg/handle/10635/97357Title: Non-Markovian environments and entanglement preservation
Authors: Tan, J.; Kyaw, T.H.; Yeo, Y.
Abstract: Using the Shabani-Lidar post-Markovian master equation, we derive non-Markovian generalizations of important quantum decohering operations on single qubits. When environmental memory effects are being taken into account, both single-qubit coherence and two-qubit entanglement may be preserved over a longer period of time, in contrast to the corresponding situations where these are totally neglected. We argue that recognizing the fact that every environment is inherently non-Markovian could be the key to the resolution of the issue of entanglement sudden death. © 2010 The American Physical Society.
Mon, 21 Jun 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/973572010-06-21T00:00:00Z