Long-Distance Entanglement of Spin Qubits via Ferromagnet

Trifunovic, Luka; Pedrocchi, Fabio L.; Loss, Daniel

doi:10.1103/physrevx.3.041023

Cited by 121 publications

(132 citation statements)

References 53 publications

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“…Approaches to implementing long-range interactions typically involve identifying a system that acts as a mediator of the interaction between the qubits, with proposed systems including optical cavities and microwave stripline resonators [21][22][23][24][25][26], floating metallic [27] and ferromagnetic [28] couplers, the collective modes of spin chains [29][30][31], superconducting systems [32,33], and multi-electron molecular cores [34]. Recently, long-range coupling of electrons located in the two outer quantum dots of a linear triple dot system has been demonstrated [35,36].…”

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confidence: 99%

Tunable Spin-Qubit Coupling Mediated by a Multielectron Quantum Dot

Srinivasa

Taylor

2015

Phys. Rev. Lett.

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We present an approach for entangling electron spin qubits localized on spatially separated impurity atoms or quantum dots via a multi-electron, two-level quantum dot. The effective exchange interaction mediated by the dot can be understood as the simplest manifestation of RudermanKittel-Kasuya-Yosida exchange, and can be manipulated through gate voltage control of level splittings and tunneling amplitudes within the system. This provides both a high degree of tuneability and a means for realizing high-fidelity two-qubit gates between spatially separated spins, yielding an experimentally accessible method of coupling donor electron spins in silicon via a hybrid impurity-dot system.Single spins in solid-state systems represent versatile candidates for scalable quantum bits (qubits) in quantum information processing architectures [1][2][3][4][5][6]. In many proposals involving single-spin qubits localized on impurity atoms [2,7] and within quantum dots [1,8], two-qubit coupling schemes harness the advantages of tunnelingbased nearest-neighbor exchange interactions: exchange gates are rapid, tunable, and protected against multiple types of noise [9][10][11][12][13]. These features have been demonstrated for electron spins in quantum dots [14][15][16][17], while a similar demonstration for spins localized on impurity atoms such as phosphorus donors in silicon remains an outstanding experimental challenge [6]. Although the exchange interaction originates from the longrange Coulomb interaction, its strength typically decays exponentially with distance [8,18]. Long-range coupling via concatenation of multiple nearest-neighbor interactions is not ideal for coupling spatially separated electron spins, as it sets a low threshold error rate below which fault-tolerant quantum computing is feasible [19,20]. A mechanism for long-range coupling that simultaneously enables scalability and robustness against errors is therefore key to realizing practical spin-based quantum information processing devices.Approaches to implementing long-range interactions typically involve identifying a system that acts as a mediator of the interaction between the qubits, with proposed systems including optical cavities and microwave stripline resonators [21][22][23][24][25][26] [32,33], and multi-electron molecular cores [34]. Recently, long-range coupling of electrons located in the two outer quantum dots of a linear triple dot system has been demonstrated [35,36]. The effective exchange interaction in that system arises from electron cotunneling between the outer dots and exhibits the fourth-order dependence on tunneling amplitudes that is characteristic of superexchange [37], but suffers from a large virtual energy cost from the doubly occupied center dot states. In contrast, a many-electron quantum dot in the center can also couple distant spins via the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, with low-energy intermediate states [38], but perhaps at the cost of low fidelity as impurityFermi sea correlations become hard to disentangle...

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mentioning

confidence: 99%

Tunable Spin-Qubit Coupling Mediated by a Multielectron Quantum Dot

Srinivasa

Taylor

2015

Phys. Rev. Lett.

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“…Note that the magnon bath considered in Ref. [16] has a dispersion which is parabolic rather than linear, as assumed in this work. For a 2D Ohmic bath (r = 0, D = 2), the function J ij (t) can be calculated as described in Ref.…”

Section: A Bath Coupling As An Entangling Gatementioning

confidence: 99%

“…Recently, the idea of performing entangling gates between qubits by coupling them to an ordered Heisenberg ferromagnet has attracted interest [16]. An ordered Heisenberg ferromagnet can be seen as a 3D magnon bath (ω k = Dk 2 ).…”

Section: Induced Interactions a Linear Dispersionmentioning

confidence: 99%

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Breakdown of surface-code error correction due to coupling to a bosonic bath

Hutter

Loss

2014

Phys. Rev. A

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We consider a surface code suffering decoherence due to coupling to a bath of bosonic modes at finite temperature and study the time available before the unavoidable breakdown of error correction occurs as a function of coupling and bath parameters. We derive an exact expression for the error rate on each individual qubit of the code, taking spatial and temporal correlations between the errors into account. We investigate numerically how different kinds of spatial correlations between errors in the surface code affect its threshold error rate. This allows us to derive the maximal duration of each quantum error correction period by studying when the single-qubit error rate reaches the corresponding threshold. At the time when error correction breaks down, the error rate in the code can be dominated by the direct coupling of each qubit to the bath, by mediated subluminal interactions, or by mediated superluminal interactions. For a 2D Ohmic bath, the time available per quantum error correction period vanishes in the thermodynamic limit of a large code size L due to induced superluminal interactions, though it does so only like

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“…A natural way to overcome such difficulties is to employ means of entangling spin qubits over long distances, which creates extra space for wiring the quantum circuits. In principle, this may be achieved by coupling the spin qubits to an electromagnetic cavity [7][8][9][10], a floating metallic gate [11], or a dipolar ferromagnet [12]. Recently, it was shown that coupling of distant spin qubits can also be realized via photon-assisted cotunneling [13].…”

Section: Introductionmentioning

confidence: 99%

Long-distance entanglement of spin qubits via quantum Hall edge states

et al. 2016

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The implementation of a functional quantum computer involves entangling and coherent manipulation of a large number of qubits. For qubits based on electron spins confined in quantum dots, which are among the most investigated solid-state qubits at present, architectural challenges are often encountered in the design of quantum circuits attempting to assemble the qubits within the very limited space available. Here, we provide a solution to such challenges based on an approach to realizing entanglement of spin qubits over long distances. We show that long-range Ruderman-Kittel-Kasuya-Yosida interaction of confined electron spins can be established by quantum Hall edge states, leading to an exchange coupling of spin qubits. The coupling is anisotropic and can be either Ising type or XY type, depending on the spin polarization of the edge state. Such a property, combined with the dependence of the electron spin susceptibility on the chirality of the edge state, can be utilized to gain valuable insights into the topological nature of various quantum Hall states.

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Long-Distance Entanglement of Spin Qubits via Ferromagnet

Cited by 121 publications

References 53 publications

Tunable Spin-Qubit Coupling Mediated by a Multielectron Quantum Dot

Tunable Spin-Qubit Coupling Mediated by a Multielectron Quantum Dot

Breakdown of surface-code error correction due to coupling to a bosonic bath

Long-distance entanglement of spin qubits via quantum Hall edge states

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