Spin-bus concept of spin quantum computing

Mehring, M.; Mende, Jens

doi:10.1103/physreva.73.052303

Cited by 54 publications

(46 citation statements)

References 36 publications

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“…This allows, for instance, to decouple electronic spin qubits from nuclear spins via spin echo techniques [3,4]. Even more remarkably, controlled manipulation of the coupled electron-nuclear system allows one to take advantage of the nuclear spin environment and use it as a long-lived quantum memory [5,6,7]. Recently, this approach has been used to demonstrate a single nuclear qubit memory with coherence times well exceeding tens of milliseconds in room temperature diamond [8].…”

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confidence: 99%

Coherence and Control of Quantum Registers Based on Electronic Spin in a Nuclear Spin Bath

et al. 2009

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We consider a protocol for the control of few-qubit registers comprising one electronic spin embedded in a nuclear spin bath. We show how to isolate a few proximal nuclear spins from the rest of the environment and use them as building blocks for a potentially scalable quantum information processor. We describe how coherent control techniques based on magnetic resonance methods can be adapted to these electronic-nuclear solid state spin systems, to provide not only efficient, high fidelity manipulation of the registers, but also decoupling from the spin bath. As an example, we analyze feasible performances and practical limitations in a realistic setting associated with nitrogen-vacancy centers in diamond.The coherence properties of isolated electronic spins in solid-state materials are frequently determined by their interactions with large ensembles of lattice nuclear spins [1,2]. The dynamics of nuclear spins is typically slow, resulting in very long correlation times of the environment. Indeed, nuclear spins represent one of the most isolated systems available in nature. This allows, for instance, to decouple electronic spin qubits from nuclear spins via spin echo techniques [3,4]. Even more remarkably, controlled manipulation of the coupled electron-nuclear system allows one to take advantage of the nuclear spin environment and use it as a long-lived quantum memory [5,6,7]. Recently, this approach has been used to demonstrate a single nuclear qubit memory with coherence times well exceeding tens of milliseconds in room temperature diamond [8]. Entangled states composed of one electronic spin and two nuclear spin qubits have been probed in such a system [9]. The essence of these experiments is to gain complete control over several nuclei by isolating them from the rest of the nuclear spin bath. Universal control of systems comprising a single electronic spin coupled to many nuclear spins has not been demonstrated yet and could enable developing of robust quantum nodes to build larger scale quantum information architectures.In this Letter, we describe a technique to achieve coherent universal control of a portion of the nuclear spin environment. In particular, we show how several of these nuclear spins can be used, together with an electronic spin, to build robust multi-qubit quantum registers. Our approach is based on quantum control techniques associated with magnetic resonance manipulation. However, there exists an essential difference between the proposed system and other previously studied small quantum processors, such as NMR molecules. Here the boundary between the qubits in the system and the bath spins is ultimately dictated by our ability to effectively control the qubits. The interactions governing the couplings of the electronic spin to the nuclear qubit and bath spins are of the same nature, so that control schemes must preserve the desired interactions among qubits while attempting to remove the couplings to the environment. The challenges to overcome are then to resolve individual energy levels ...

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confidence: 99%

Coherence and Control of Quantum Registers Based on Electronic Spin in a Nuclear Spin Bath

et al. 2009

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“…Here we show how to exploit a local, isolated electron spin to coherently control nuclear spins. Moreover, we suggest that this approach provides a fast and reliable means of controlling nuclear spins and enables the electron spins of such solid-state systems to be used for state preparation and readout [9] of nuclear spin states, and additionally as a spin actuator for mediating nuclear-nuclear spin gates.…”

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confidence: 99%

Universal control of nuclear spins via anisotropic hyperfine interactions

et al. 2008

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We show that nuclear spin subsystems can be completely controlled via microwave irradiation of resolved anisotropic hyperfine interactions with a nearby electron spin. Such indirect addressing of the nuclear spins via coupling to an electron allows us to create nuclear spin gates whose operational time is significantly faster than conventional direct addressing methods. We experimentally demonstrate the feasibility of this method on a solid-state ensemble system consisting of one electron and one nuclear spin.Coherent control of quantum systems promises optimal computation [1], secure communication [2], and new insight into the fundamental physics of many-body problems [3]. Solid-state proposals [4,5,6,7,8] for such quantum information processors employ isolated spin degrees of freedom which provide Hilbert spaces with long coherence times. Here we show how to exploit a local, isolated electron spin to coherently control nuclear spins. Moreover, we suggest that this approach provides a fast and reliable means of controlling nuclear spins and enables the electron spins of such solid-state systems to be used for state preparation and readout [9] of nuclear spin states, and additionally as a spin actuator for mediating nuclear-nuclear spin gates.Model System. The spin Hamiltonian of a single local electron spin with angular momentum, S = 1 2 and N nuclear spins, each with angular momentum I k = 1 2 , in the presence of a magnetic field B is [10]:Here β e is the Bohr magneton, γ k n is the gyromagnetic ratio;Ŝ andÎ k are the spin-1 2 operators. The secondrank tensors g, A k , δ, and D kl represent the electron gfactor, the hyperfine interaction, the chemical shift, and the nuclear dipole-dipole interaction respectively.In the regime where the static magnetic field B = B 0ẑ provides a good quantization axis for the electron spin, the Hamiltonian can be simplified by dropping the nonsecular terms which corresponds to keeping only electron interactions involving S z . The quantization axis of any nuclear spin depends on the magnitudes of the hyperfine interaction and the main magnetic field, as well as their relative orientations. When these two fields are comparable in magnitude [37] H 0 can be approximated by: (2) with N=1. The electron spin state is in an eigenstate of purely the Zeeman interaction, while the nuclear spin state is not an eigenfunction of the Zeeman interaction alone due to the anisotropic hyperfine interaction. Because α0|β1 = 0 and α0|β0 = 0 the electron spin operator (Ŝx) has finite probabilities between all levels (dashed arrows). This allows for universal control of the entire spin system. The filled and unfilled circles represent the relative spin state populations of the ensemble at thermal equilibrium. In our experimental setup the energy differences are ω12/2π = 7.8 MHz, ω34/2π = 40 MHz, ω14/2π = 12.005 GHz, ω23/2π = 11.954GHzThe nuclear dipole-dipole interaction is neglected as it is typically 10 2 times weaker than the hyperfine terms.As described in Figure 1 (N=1), the nuclear spin is qu...

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“…If the output state is |0 N Ò ) f(x) is constant or else f(x) is balanced. Figure 6 (bottom) shows the diagonal values of the output density matrix of the two qubit Deutsch algorithm demonstrated in a solid state qubyte +1 system [9,10]. Note that 0000 f results in out |00 ψ = Ò as expected for a constant function whereas the other three output states are out {|01 , | 10 , | 11 } ψ = Ò Ò Ò as is expected for these balanced functions.…”

Section: Deutsch's Algorithmmentioning

confidence: 91%