Experimental detection of quantum information sharing and its quantification in quantum spin systems

Das, Debashish; Singh, Harkirat; Chakraborty, Tanmoy; Gopal, Radha Krishna; Mitra, Chiranjib

doi:10.1088/1367-2630/15/1/013047

Cited by 33 publications

(44 citation statements)

References 41 publications

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“…Alternating antiferromagnetic spin 1/2 chains and ladders exhibit spin dimers as the ground state. In particular, Cu(NO 3 ) 2 · 2.5D 2 O and NH 4 CuPO 4 · H 2 O have been used to quantify entanglement by using magnetic susceptibility [17][18][19][20][21] and heat capacity 19,22-24 as entanglement witnesses. Another way to detect entanglement is to induce a quantum phase transition by, for instance, the application of a magnetic field, as sketched in Fig.…”

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Experimental realization of long-distance entanglement between spins in antiferromagnetic quantum spin chains

Sahling¹,

Reményi²,

Paulsen³

et al. 2015

Nature Phys

125

108

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Entanglement is a concept that has defied common sense since the discovery of quantum mechanics. Two particles are said to be entangled when the quantum state of each particle cannot be described independently, no matter how far apart in space and time the two particles are. We demonstrate experimentally that unpaired spins separated by several hundred ångström entangle through a collection of spin singlets made up of antiferromagnetic spin-1/2 chains in a bulk material. Low-temperature magnetization and specific heat studies as a function of magnetic field reveal the occurrence of very dilute spin dimers and at least two quantum phase transitions related to the breaking of excited local triplets. The mechanism at the origin of the unpaired spins inside the quantum chains is the inter-modulation potential between two sublattices, and may be replicated using well-designed synthetic multilayers. E ntanglement is an essential feature of the macroscopic world 1 , despite the fact that human perception has difficulty accepting such strange predictions. A very fruitful area of research today is quantum computing technology, where entanglement is being harnessed for eventual use in quantum computation and communications 2,3 . Scientists are also developing new areas of research where entanglement could lie at the origin of the interactions in ever larger objects, ranging from photons to clusters of atoms to molecules-and even to cosmological objects.Most of the protocols for quantum communication rely on entangled photons 4 , as they are weakly interacting and can be easily manipulated using existing optical fibre technology. However, it is not always convenient to use photons to exchange information as, in particular, it is not straightforward to convert information between physically different qubits. Another approach described in seminal papers by Bose 5,6 suggested the use of spin chains as quantum channels for short-or mid-range communication, showing that, by means of the magnetic interaction between the spins that compose the chain, the transfer of information arises naturally as the system evolves dynamically, without the requirement for any external control. Transferring quantum information between distant qubits through spin chains would be highly desirable. However, this procedure often requires the repeated application of swapping gates and is, consequently, very demanding experimentally. Moreover, the features that characterize the transmission, such as teleportation, fidelity, transfer quality and speed, depend on the properties of the underlying quantum system 2,3 .Other developments have explored the conditions for longdistance entanglement without the need to perform operations and measurements. Among the many possible spin configurations it seems that antiferromagnetic spin arrays characterized by spin gaps above the ground state can exhibit true entanglement over long distances 7 . Furthermore, the entanglement is a slowly decreasing function of distance, allowing robust teleportation across finite di...

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“…1c. One of the components of the triplet mixes with the ground state singlet, the entangled state de-coheres and the entanglement decays analytically on approaching the critical magnetic field 21,25,26 . Beyond that critical field the magnetization and specific heat dependences with temperature follow the known laws for unpaired spins (Supplementary Methods).…”

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confidence: 99%

Experimental realization of long-distance entanglement between spins in antiferromagnetic quantum spin chains

Sahling¹,

Reményi²,

Paulsen³

et al. 2015

Nature Phys

125

108

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“…Simultaneously, there is also unabated interest in quantum entanglement of spin qubits, see for example [3][4][5][6]. Therefore it seems that simple formulae which describe the entanglement in the case of states accessible in the lab may be very useful and allow experimentalists to develop their experimental intuition.…”

Section: Introductionmentioning

confidence: 99%

System Size Dependence of Entanglement in Quantum One-Dimensional Models

Jakubczyk

2017

Acta Phys. Pol. A

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We show that entanglement in one-dimensional spin and electron systems, with one excitation, depends only on the system size and has very simple form in both multipartite and bipartite case. Regarding the multipartite case, we present very simple expressions for global entanglement and N -concurrence, and show that they are mutually related. In the bipartite case, we give expressions for I-concurrence and negativity, and show that they are also dependent on each other.

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“…Furthermore, RVB states have also been proposed as robust basis states for topological quantum computation [11]. As regards examples of real systems, valence-bond state (composed of alternating dimer spin chain) has been experimentally realized in the spin-chain compound, copper nitrate (CuðNO 3 Þ 2 Â 2:5H 2 O) [12]; RVB state occurs naturally in SrCu 2 ðBO 3 Þ 2 [13] which can be explained by the Shastry-Sutherland model [14]; valence bond solid has been observed in Zn x Cu 4 À x ðODÞ 6 Cl 2 [15].…”

Section: Introductionmentioning

confidence: 99%

Study of two-spin entanglement in singlet states

Lone

Dey

Yarlagadda

2015

Solid State Communications

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a b s t r a c tWe study the entanglement properties of two-spin subsystems in spin-singlet states. The average entanglement between two spins is maximized in a single valence-bond (VB) state. On the other hand, E v 2 (the average entanglement between a subsystem of two spins and the rest of the system) can be maximized through a homogenized superposition of the VB states. The maximal E v 2 rapidly increases with system size and saturates at its maximum allowed value. We adopt two ways of obtaining maximal E v 2 states: (1) imposing homogeneity on singlet states; and (2) generating isotropy in a general homogeneous state. By using these two approaches, we construct explicitly four-spin and six-spin highly entangled states that are both isotropic and homogeneous. Our maximal E 2 v states represent a new class of resonating-valence-bond states which we show to be the ground states of the infinite-range Heisenberg model.

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Experimental detection of quantum information sharing and its quantification in quantum spin systems

Cited by 33 publications

References 41 publications

Experimental realization of long-distance entanglement between spins in antiferromagnetic quantum spin chains

Experimental realization of long-distance entanglement between spins in antiferromagnetic quantum spin chains

System Size Dependence of Entanglement in Quantum One-Dimensional Models

Study of two-spin entanglement in singlet states

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