Environment-Induced Sudden Death of Entanglement

Almeida, M. P.; Melo, Fernando de; Hor-Meyll, M.; Salles, A.; Walborn, S. P.; Ribeiro, P. H. Souto; Davidovich, L.

doi:10.1126/science.1139892

Cited by 922 publications

(783 citation statements)

References 16 publications

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“…We can draw two important conclusions from the result in equation (3). First, C r is always larger than C d , which means that weak measurement and quantum measurement reversal indeed can be used for protecting entanglement from decoherence.…”

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confidence: 89%

Protecting entanglement from decoherence using weak measurement and quantum measurement reversal

et al. 2011

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Decoherence, often caused by unavoidable coupling with the environment, leads to degradation of quantum coherence 1 . For a multipartite quantum system, decoherence leads to degradation of entanglement and, in certain cases, entanglement sudden death 2,3 . Tackling decoherence, thus, is a critical issue faced in quantum information, as entanglement is a vital resource for many quantum information applications including quantum computing 4 , quantum cryptography 5 , quantum teleportation 6-8 and quantum metrology 9 . Here, we propose and demonstrate a scheme to protect entanglement from decoherence. Our entanglement protection scheme makes use of the quantum measurement itself for actively battling against decoherence and it can effectively circumvent even entanglement sudden death.One way to cope with decoherence is to make use of entanglement distillation protocols by which a pure maximally entangled state may be obtained from multiple copies of partially decohered states 4,10-14 . Note, however, that it is impossible to obtain an entangled state from copies of fully decohered (that is, separable) states by applying entanglement distillation 15 . Another method to deal with decoherence is to rely on the so-called decoherence-free subspace 16,17 . The decoherence-free subspace, however, requires the interaction Hamiltonian to have an appropriate symmetry, which might not always be present. The quantum Zeno effect may also be used to suppress decoherence 18,19 as well as to generate entanglement 20 under some specific situations.Our scheme for protecting entanglement from decoherence is based on the fact that weak quantum measurement can be reversed. The reversibility of weak quantum measurement was originally discussed in the context of quantum error correction 21 and was demonstrated for a single superconducting qubit and a single photonic qubit [22][23][24] . Recently, it was shown that weak measurement and quantum measurement reversal can effectively suppress amplitude-damping decoherence for a single qubit 25,26 . Here, we experimentally demonstrate a scheme for protecting entanglement from amplitude-damping decoherence using weak measurement and quantum measurement reversal. The scheme can reduce or even completely nullify the effect of decoherence as evidenced by increased concurrence of the two-qubit system.Consider a two-level quantum system (S) whose computational bases are |0 S and |1 S . The environment (E) is initially at |0 E . Amplitude-damping decoherence, in which a particular computational basis state is irreversibly and probabilistically transferred to the other, results from state-dependent coupling of the system qubit to the environment and is described by the following quantum map,where 0 ≤ D ≤ 1 is the magnitude of the decoherence andAmplitude-damping decoherence is highly relevant for many practical qubit systems. For instance, amplitudedamping decoherence is caused by photon loss for the vacuumsingle-photon qubit, by spontaneous decay for the atomic energy level qubit and by zero-temperat...

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confidence: 89%

Protecting entanglement from decoherence using weak measurement and quantum measurement reversal

et al. 2011

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“…This signifies a "sudden death of (non-local) entanglement" whereas the decay characteristics of local decoherence is exponential. Finite-time disentanglement has also been observed in a recent experiment [16]. In the following we study the disentanglement of the state ρ cav,f .…”

Section: Finite-time Disentanglementmentioning

confidence: 93%

“…For the non-trivial class of states discussed here, this can even occur during finite time. This phenomena of "sudden death of entanglement" has been investigated theo-retically for a conventional cavity QED setup [15] and observed in an experiment as well [16].…”

Section: Introductionmentioning

confidence: 99%

Entanglement and disentanglement in circuit QED architectures

Zueco¹,

Reuther²,

Hänggi³

et al. 2010

Physica E: Low-dimensional Systems and Nanostructures

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We propose a protocol for creating entanglement within a dissipative circuit QED network architecture that consists of two electromagnetic circuits (cavities) and two superconducting qubits. The system interacts with a quantum environment, giving rise to decoherence and dissipation. We discuss the preparation of two separate entangled cavityqubit states via Landau-Zener sweeps, after which the cavities interact via a tunable "quantum switch" which is realized with an ancilla qubit. Moreover, we discuss the decay of the resulting entangled two-cavity state due to the influence of the environment, where we focus on the entanglement decay.

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“…It has been shown that in some cases entanglement can completely disappear in finite times. This phenomenon is known as entanglement sudden death (ESD) [7][8][9][10] and has been observed experimentally by Almeida et al [11]. It is of clear relevance to study and understand ESD and related phenomena occurring during the evolution of open quantum systems, because the actual implementation of quantum computation and other quantum information tasks depend on the longevity of entanglement in multiqubits states.…”

Section: Introductionmentioning

confidence: 99%