Topological Hunds rules and the electronic properties of a triple lateral quantum dot molecule

Korkusiński, Marek; Gimenez, I. Puerto; Hawrylak, Paweł; Gaudreau, Louis; Studenikin, Sergei; Sachrajda, Andrew

doi:10.1103/physrevb.75.115301

Cited by 111 publications

(152 citation statements)

References 40 publications

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“…This reduces to a multi-orbital Hubbard model for a linear three-site system in the four-electron regime [41,42]. We assume gate voltages can be applied to the system such that the total electron number can be set to be four, while the charge stability diagram prefers the initial configuration of (1, 2, 1).…”

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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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confidence: 99%

Tunable Spin-Qubit Coupling Mediated by a Multielectron Quantum Dot

Srinivasa

Taylor

2015

Phys. Rev. Lett.

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“…In a more elaborate model, we could expand this to include the following terms U 0 j=1,2,3 n j↑ n j ↓ + U 1 j=1,2 n j n j+1 + U 2 n 1 n 3 , (A12) corresponding to double-occupations, nearest-neighbor couplings, and next-nearest-neighbor couplings. Such models have previously been explored by some authors, 6,14,34 while other authors consider a basis set of singly-occupied states, 5 where all the Coulomb terms are incorporated into the exchange interaction parameters of an effective Hamiltonian.…”

Section: Appendix A: Calculation Detailsmentioning

confidence: 99%

Characterizing gate operations near the sweet spot of an exchange-only qubit

et al. 2015

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Optimal working points or "sweet spots" have arisen as an important tool for mitigating charge noise in quantum dot logical spin qubits. The exchange-only qubit provides an ideal system for studying this effect because Z rotations are performed directly at the sweet spot, while X rotations are not. Here for the first time we quantify the ability of the sweet spot to mitigate charge noise by treating X and Z rotations on an equal footing. Specifically, we optimize X rotations and determine an upper bound on their fidelity. We find that sweet spots offer a fidelity improvement factor of at least 20 for typical GaAs devices, and more for Si devices.

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“…Since electrons are well localized in each QD, a system of two TQDs in a chain can be described by an extended Hubbard model. 35 With c i † ͑c i ͒ electron creation ͑annihilation͒ operator for the electron with spin = Ϯ 1 on the ith QD, the Hubbard Hamiltonian reads…”

Section: Modelmentioning

confidence: 99%

Quantum circuits based on coded qubits encoded in chirality of electron spin complexes in triple quantum dots

Hsieh

Hawrylak

2010

Phys. Rev. B

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We present a theory of quantum circuits based on coded qubits encoded in chirality of electron spin complexes in lateral gated semiconductor triple quantum dot molecules with one-electron spin in each dot. Using microscopic Hamiltonian we show how to initialize, coherently control, and measure the quantum state of a chirality-based coded qubit using static magnetic field and voltage tuning of individual dots. The microscopic model of two interacting coded qubits is established and mapped to an Ising Hamiltonian, resulting in nonlocal double-qubit gates.

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Topological Hunds rules and the electronic properties of a triple lateral quantum dot molecule

Cited by 111 publications

References 40 publications

Tunable Spin-Qubit Coupling Mediated by a Multielectron Quantum Dot

Tunable Spin-Qubit Coupling Mediated by a Multielectron Quantum Dot

Characterizing gate operations near the sweet spot of an exchange-only qubit

Quantum circuits based on coded qubits encoded in chirality of electron spin complexes in triple quantum dots

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