A triangular triple quantum dot with tunable tunnel couplings

Noiri, Akito; Kawasaki, Kento; Otsuka, Takeshi; Nakajima, Takashi; Yoneda, Jun; Amaha, S.; Delbecq, Matthieu; Takeda, Kenta; Allison, Giles; Ludwig, Arne; Wieck, A. D.; Tarucha, Seigo

doi:10.1088/1361-6641/aa7596

Cited by 27 publications

(24 citation statements)

References 32 publications

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“…Quantum dot systems have already achieved success in realising simulations of Mott-insulator physics in linear arrays [28]. Additionally, the feasibility to extend these systems into 2D lattices has recently been demonstrated [4,[29][30][31][32], including the ability to perform measurements of spin correlations [4]. As a result, quantum dot systems are now prime candidates for exploring how superconductivity and magnetism emerge in strongly-correlated electron systems [33][34][35].The emergence of magnetism in purely itinerant electron systems presents a long-standing problem in quantum many-body physics [2,3] with only few rigorous theoretical results, for instance in systems with special flat bands or Nagaoka's ferromagnetism (see Ref.[36] and references therein).…”

mentioning

confidence: 99%

Nagaoka ferromagnetism observed in a quantum dot plaquette

Dehollain

Mukhopadhyay

Michal

et al. 2020

Nature

115

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Engineered, highly-controllable quantum systems hold promise as simulators of emergent physics beyond the capabilities of classical computers [1]. An important problem in many-body physics is itinerant magnetism, which originates purely from long-range interactions of free electrons and whose existence in real systems has been subject to debate for decades [2,3]. Here we use a quantum simulator consisting of a four-site square plaquette of quantum dots [4] to demonstrate Nagaoka ferromagnetism [5]. This form of itinerant magnetism has been rigorously studied theoretically [6][7][8][9] but has remained unattainable in experiment. We load the plaquette with three electrons and demonstrate the predicted emergence of spontaneous ferromagnetic correlations through pairwise measurements of spin. We find the ferromagnetic ground state is remarkably robust to engineered disorder in the on-site potentials and can induce a transition to the low-spin state by changing the plaquette topology to an open chain. This demonstration of Nagaoka ferromagnetism highlights that quantum simulators can be used to study physical phenomena that have not yet been observed in any system before. The work also constitutes an important step towards large-scale quantum dot simulators of correlated electron systems.The potential impact of discovering and understanding exotic forms of magnetism and superconductivity is one of the largest motivations for research in condensedmatter physics. These quantum mechanically governed effects result from the strong correlations that arise between interacting electrons. Modelling and simulating such systems can in some instances only be achieved through the use of engineered, controllable systems that operate in the quantum regime [1]. Efforts to build quantum simulators have already demonstrated great promise at this early stage [10], mainly led by the ultracold atom * These authors contributed equally to this work. † e-mail: l.m.k.vandersypen@tudelft.nl community [11-17]. More broadly, quantum simulations of many-body fermionic systems have been carried out in a range of experimental systems such as quantum dot lattices [18], dopant atoms [19], superconducting circuits [20] and trapped ions [21]. Electrostatically defined semiconductor quantum dots [22][23][24] have been proposed as excellent candidates for quantum simulations [25][26][27]. Their ability to reach thermal energies far below the hopping and on-site interaction energies enable access to previously unexplored material phases. Quantum dot systems have already achieved success in realising simulations of Mott-insulator physics in linear arrays [28]. Additionally, the feasibility to extend these systems into 2D lattices has recently been demonstrated [4,[29][30][31][32], including the ability to perform measurements of spin correlations [4]. As a result, quantum dot systems are now prime candidates for exploring how superconductivity and magnetism emerge in strongly-correlated electron systems [33][34][35].The emergence of magnetism in purely i...

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mentioning

confidence: 99%

Nagaoka ferromagnetism observed in a quantum dot plaquette

Dehollain

Mukhopadhyay

Michal

et al. 2020

Nature

115

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“…On the other hand, experiments with quantum dots are still mainly being performed with linear arrays with no more than a few sites 9,16,17 . Efforts to go beyond 1D with quantum dot arrays have so far stopped short of achieving well-characterized tunnel couplings in the few-electron regime [18][19][20] .…”

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confidence: 99%

A 2 × 2 quantum dot array with controllable inter-dot tunnel couplings

Mukhopadhyay

Dehollain

Reichl

et al. 2018

Applied Physics Letters

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The interaction between electrons in arrays of electrostatically defined quantum dots is naturally described by a Fermi-Hubbard Hamiltonian. Moreover, the high degree of tunability of these systems make them a powerful platform to simulate different regimes of the Hubbard model. However, most quantum dot array implementations have been limited to one-dimensional linear arrays. In this letter, we present a square lattice unit cell of 2×2 quantum dots defined electrostatically in a AlGaAs/GaAs heterostructure using a double-layer gate technique. We probe the properties of the array using nearby quantum dots operated as charge sensors. We show that we can deterministically and dynamically control the charge occupation in each quantum dot in the single-to few-electron regime. Additionally, we achieve simultaneous individual control of the nearest-neighbor tunnel couplings over a range 0-40 µeV. Finally, we demonstrate fast (∼ 1 µs) single-shot readout of the spin state of electrons in the dots, through spin-to-charge conversion via Pauli spin blockade. These advances pave the way to analog quantum simulations in two dimensions, not previously accessible in quantum dot systems.

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“…Already concerning the device design, where DQDs are limited to serial and parallel configurations, a new opportunity arises. TQDs can be arranged in a triangular configuration, where each QD can be tunnel coupled to both others.…”

Section: Triple Quantum Dotmentioning

confidence: 99%

Charge Reconfiguration in Isolated Quantum Dot Arrays

et al. 2019

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A high level of tunability and control over arrays of quantum dots are key ingredients toward the goal of scalable-based qubit architectures. Increasing array size simultaneously increases the parameter space and therefore the tuning complexity. The electron reconfiguration behavior of quantum dot arrays isolated from the electron reservoirs is studied experimentally. Isolating a quantum dot array from the reservoirs does not only enable a high degree of control over the tunnel couplings but at the same time drastically simplifies the stability diagrams for small numbers of electrons trapped in the array. Experimental results on double, triple, and quadruple quantum dot arrays are presented and complementary model calculations allow the identification of all transitions observed in the experiment. Highly tunable long-range transitions are observed in isolated triple quantum dots and evidence of higher-order cotunneling is found for the quadruple quantum dot array.

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A triangular triple quantum dot with tunable tunnel couplings

Cited by 27 publications

References 32 publications

Nagaoka ferromagnetism observed in a quantum dot plaquette

Nagaoka ferromagnetism observed in a quantum dot plaquette

A 2 × 2 quantum dot array with controllable inter-dot tunnel couplings

Charge Reconfiguration in Isolated Quantum Dot Arrays

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