Long-range interactions and information transfer in spin chains

Ronke, Rebecca; Spiller, Timothy P.; D’Amico, Irene

doi:10.1088/1742-6596/286/1/012020

Cited by 6 publications

(5 citation statements)

References 13 publications

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“…We now relax this assumption and include all pairwise couplings with a dipole-dipole interaction 1/r 3 distance dependence (similar to Refs. [35,36]), including register to chain spin couplings. All spins are assumed equally spaced, with the coupling strength for nearest neighbors being 26 kHz.…”

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Practicality of Spin Chain Wiring in Diamond Quantum Technologies

et al. 2013

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Coupled spin chains are promising candidates for 'wiring up' qubits in solid-state quantum computing (QC). In particular, two nitrogen-vacancy centers in diamond can be connected by a chain of implanted nitrogen impurities; when driven by a suitable global fields the chain can potentially enable quantum state transfer at room temperature. However, our detailed analysis of error effects suggests that foreseeable systems may fall far short of the fidelities required for QC. Fortunately the chain can function in the more modest role as a mediator of noisy entanglement, enabling QC provided that we use subsequent purification. For instance, a chain of 5 spins with inter-spin distances of 10 nm has finite entangling power as long as the T2 time of the spins exceeds 0.55 ms. Moreover we show that re-purposing the chain this way can remove the restriction to nearest-neighbor interactions, so eliminating the need for complicated dynamical decoupling sequences.Spin chains with nearest neighbor XY coupling mediate coherent interactions between distant spin qubits with fixed locations, and can thus serve as channels to transfer quantum information [1][2][3]. An important application would be to interconnect distant sub-registers of parallel parts in a scalable, solid-state quantum computer [4], e.g. in a diamond-based architecture at room temperature [5]. With an observed roomtemperature coherence time of 1.8 ms [6], the electron spin of individual nitrogen-vacancy (NV − ) defects in diamond is a promising candidate for a qubit [7]: Initialisation, coherent manipulation and measurement with nanoscale resolution (∼ 150 nm) have already been experimentally demonstrated using optical techniques under ambient conditions [8]. In addition, the long-lived 15 N nuclear spin (I = 1/2) associated with each NV − center can act as a local, coherent memory, accessible via the hyperfine coupling [9, 10]. A universal set of quantum operations between the nuclear memory spin and the processing electronic spin qubit within each NV − center is available with microwave and radio-frequency pulses [11][12][13]. Two NV − centers with only a small separation (r 10 nm) may be entangled through direct electron spin dipole-dipole coupling as long as a T 2 time on the order of milliseconds can be maintained [14]. However, individual addressability of the NV − center qubits demands larger separations of several tens or hundreds of nanometers [8], and the direct interaction becomes too weak.A recent proposal [15] suggested a chain of N implanted nitrogen impurities (each with a "dark" electronic spin-1/2) as a coherent quantum channel to transfer quantum states between distant NV − centers at room-temperature (see Fig. 1a). Here, the electron spins of the NV − centers and the nitrogen impurities interact with each other through nearest-neighbor dipoledipole coupling [16, 17]. Importantly, the scheme does not require individual control of the chain spins, instead relying on global resonant driving fields to turn the effective Hamiltonian into an XY exc...

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Practicality of Spin Chain Wiring in Diamond Quantum Technologies

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“…Using concatenation, we can eliminate all interactions in the spin chain except for, e.g., nearest-neighbor interactions. This Hamiltonian is vital not only for simulation of quantum magnetism, but also many other quantum information protocols [42,43].…”

Section: Example Programsmentioning

confidence: 99%

Programmable quantum simulation by dynamic Hamiltonian engineering

2014

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Quantum simulation is a promising near term application for quantum information processors with the potential to solve computationally intractable problems using just a few dozen interacting qubits [1,2,3]. A range of experimental platforms have recently demonstrated the basic functionality of quantum simulation applied to quantum magnetism, quantum phase transitions, and relativistic quantum mechanics [4,5,6,7,8,9,10,11]. However, in all cases, the physics of the underlying hardware restricts the achievable inter-particle interactions and forms a serious constraint on the versatility of the simulators. To broaden the scope of these analog devices, we develop a suite of pulse sequences that permit a user to efficiently realize average Hamiltonians that are beyond the native interactions of the system [12,13]. Specifically, this approach permits the generation of all symmetrically coupled translation-invariant two-body Hamiltonians with homogeneous on-site terms, a class which includes all spin-1/2 XYZ chains, but generalized to include long-range couplings. Our work builds on previous work proving that universal simulation is possible using both entangling gates and single-qubit unitaries [14,15,16]. We show that determining the appropriate "program" of unitary pulse sequences which implements an arbitrary Hamiltonian transformation can be formulated as a linear program over functions defined by those pulse sequences, running in polynomial time and scaling efficiently in hardware resources. Our analysis extends from circuit model quantum information to adiabatic quantum evolutions, representing an important and broad-based success in applying functional analysis to the field of quantum information.

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“…What their influences on the fidelity of state transfer are [16], [22] and how to correct or circumvent them [6] , [20] has been the object of various studies. We shall here relate particularly to the errors imputable to the quantum wires and measurements.…”

Section: Introductionmentioning

confidence: 99%

Almost perfect state transfer in quantum spin chains

Vinet

Zhedanov²

2012

Phys. Rev. A

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The natural notion of almost perfect state transfer (APST) is examined. It is applied to the modelling of efficient quantum wires with the help of XX spin chains. It is shown that APST occurs in mirror-symmetric systems, when the 1-excitation energies of the chains are linearly independent over rational numbers. This result is obtained as a corollary of the Kronecker theorem in Diophantine approximation. APST happens under much less restrictive conditions than perfect state transfer (PST) and moreover accommodates the unavoidable imperfections. Some examples are discussed.

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Long-range interactions and information transfer in spin chains

Cited by 6 publications

References 13 publications

Practicality of Spin Chain Wiring in Diamond Quantum Technologies

Practicality of Spin Chain Wiring in Diamond Quantum Technologies

Programmable quantum simulation by dynamic Hamiltonian engineering

Almost perfect state transfer in quantum spin chains

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