Site-Selective Quantum Control in an Isotopically Enriched 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mmultiscripts><mml:mi>Si</mml:mi><mml:mprescripts /><mml:none /><mml:mn>28</mml:mn></mml:mmultiscripts><mml:mo>/</mml:mo><mml:msub><mml:mi>Si</mml:mi><mml:mrow><mml:mn>0.7</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Ge</mml:mi><mml:mrow><mml:mn>0.3</mml:mn></mml:mrow></mml:msub></mml:math>
 Quadruple Quantum Dot

Sigillito, A. J.; Loy, James C.; Zajac, DM; Gullans, Michael; Edge, L. F.; Petta, J. R.

doi:10.1103/physrevapplied.11.061006

Cited by 72 publications

(55 citation statements)

References 49 publications

(80 reference statements)

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confidence: 99%

“…Through coherent spin transport, our resonant SWAP gate enables the coupling of non-adjacent qubits, thus paving the way to large scale experiments using silicon spin qubits.In this work, we use two sites of a quadruple quantum dot fabricated on a 28 Si/SiGe heterostructure [inset of Fig. 1(a)] [8]. Electric dipole spin resonance (EDSR) [14,15] enables single-spin control and an on-chip micromagnet detunes the frequency of each spin to enable site-selective control [8,16].…”

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confidence: 99%

“…1(a)] [8]. Electric dipole spin resonance (EDSR) [14,15] enables single-spin control and an on-chip micromagnet detunes the frequency of each spin to enable site-selective control [8,16]. For demonstration purposes, we use two dots in the device with qubits accumulated under plunger gates P 3 and P 4 .…”

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confidence: 99%

“…where γ e is the electronic gyromagnetic ratio and B tot i is the magnetic field at dot i, the two qubits directly undergo SWAP oscillations [9,[19][20][21]. However, state-of-the-art devices rely on large magnetic field gradients [2,3,6,8] and our device has γ e B tot 3 = 16.949 GHz and γ e B tot 4 = 17.089 GHz at an external magnetic field of 410 mT. In this regime, the exchange interaction leads to a CPHASE-like evolution [3,22,23].…”

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Coherent transfer of quantum information in a silicon double quantum dot using resonant SWAP gates

et al. 2019

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Solid state quantum processors based on spins in silicon quantum dots are emerging as a powerful platform for quantum information processing [1][2][3]. High fidelity single-and two-qubit gates have recently been demonstrated [2][3][4][5][6] and large extendable qubit arrays are now routinely fabricated [7,8]. However, two-qubit gates are mediated through nearest-neighbor exchange interactions [1,9], which require direct wavefunction overlap. This limits the overall connectivity of these devices and is a major hurdle to realizing error correction [10], quantum random access memory [11], and multi-qubit quantum algorithms [12]. To extend the connectivity, qubits can be shuttled around a device using quantum SWAP gates, but phase coherent SWAPs have not yet been realized in silicon devices [2][3][4][5][6]. Here, we demonstrate a new single-step resonant SWAP gate. We first use the gate to efficiently initialize and readout our double quantum dot. We then show that the gate can move spin eigenstates in 100 ns with average fidelityF (p) SWAP = 98 %. Finally, the transfer of arbitrary two-qubit product states is benchmarked using state tomography and Clifford randomized benchmarking [5,13], yielding an average fidelity ofF (c) SWAP = 84 % for gate operation times of ∼300 ns. Through coherent spin transport, our resonant SWAP gate enables the coupling of non-adjacent qubits, thus paving the way to large scale experiments using silicon spin qubits.In this work, we use two sites of a quadruple quantum dot fabricated on a 28 Si/SiGe heterostructure [inset of Fig. 1(a)] [8]. Electric dipole spin resonance (EDSR) [14,15] enables single-spin control and an on-chip micromagnet detunes the frequency of each spin to enable site-selective control [8,16]. For demonstration purposes, we use two dots in the device with qubits accumulated under plunger gates P 3 and P 4 . We hereafter refer to the two qubits as Q 3 and Q 4 , respectively. The charge stability diagram of this DQD is shown in Fig. 1(a) and quantum control is performed in the (N i , N i+1 ) = (1, 1) charge configuration, where N i denotes the number of electrons on dot i. We measure the state of Q 4 through spin-selective tunneling to a drain reservoir accumulated beneath gate D 3 [17].There are two modes of operation for the resonant SWAP gate demonstrated in this Letter. First, a projection-SWAP can be used to transfer spin eigenstates Figure 1. (a) Charge stability map for a DQD formed using sites 3 and 4 in the quadruple dot array (inset). Quantum control is performed near the center of the (1,1) charge stability region as denoted by the green circle. Readout of dot 4 is performed at the (1,0)-(1,1) charge transition denoted by the blue triangle. (b) The typical measurement cycle is shown for controlling and reading out two quantum dots. In panel A, the qubits are manipulated and in panel B Q4 is read out through spin-selective tunneling -leaving the qubit in the |↓ state. In panel C, the exchange interaction J34 between Q3 and Q4 is modulated (through modulation of...

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Coherent transfer of quantum information in a silicon double quantum dot using resonant SWAP gates

et al. 2019

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“…Following the recent progress in constructing high-fidelity single-qubit and two-qubit gate operations with electron spins [6][7][8][9][10][11] , there are increasing efforts towards scaling to larger multi-qubit devices [12][13][14][15] . One of the key challenges in scaling up spin qubits is developing the software tools necessary to keep pace with increasingly complex devices.…”

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Computer-automated tuning procedures for semiconductor quantum dot arrays

Mills

Feldman

Monical

et al. 2019

Applied Physics Letters

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As with any quantum computing platform, semiconductor quantum dot devices require sophisticated hardware and controls for operation. The increasing complexity of quantum dot devices necessitates the advancement of automated control software and image recognition techniques for rapidly evaluating charge stability diagrams. We use an image analysis toolbox developed in Python to automate the calibration of virtual gates, a process that previously involved a large amount of user intervention. Moreover, we show that straightforward feedback protocols can be used to simultaneously tune multiple tunnel couplings in a triple quantum dot in a computer automated fashion. Finally, we adopt the use of a 'tunnel coupling lever arm' to model the interdot barrier gate response and discuss how it can be used to more rapidly tune interdot tunnel couplings to the GHz values that are compatible with exchange gates.Quantum processors rely on classical hardware and controls in order to prepare, manipulate, and measure qubit states. For this reason, it is advantageous to develop tools to automate the operation of small quantum processors and routinely tune-up single qubit and two-qubit gates to maintain high performance 1-3 . Semiconductor spin qubits are a promising platform for realizing quantum computation largely due to their potential for scaling 4 . To tune up semiconductor quantum dots for operation as spin qubits requires control over the ground state charge occupation and chemical potential of each dot, as well as the interdot tunnel couplings 5 .Following the recent progress in constructing high-fidelity single-qubit and two-qubit gate operations with electron spins 6-11 , there are increasing efforts towards scaling to larger multi-qubit devices 12-15 . One of the key challenges in scaling up spin qubits is developing the software tools necessary to keep pace with increasingly complex devices. To date, approaches to implementing automated control software during tune-up of semiconductor qubits include training neural networks to identify the state of a device 16 , experimentally realizing automated control procedures for tuning double quantum dot (DQD) devices into the single-electron regime 17 , and automatically tuning the interdot tunnel coupling in a DQD [18][19][20] .In this Letter, we use an image analysis toolbox developed at Sandia National Laboratories to accurately analyze charge stability diagrams acquired from a triple quantum dot (TQD) unit cell of a 9-dot linear array 13,21 . Computer automated analysis of charge stability diagrams performs the inversion of the device capacitance matrix and the establishment of 'virtual gates'. Virtual gates compensate for cross-capacitances in the device and allow the chemical potential of each dot in the array to be independently controlled 13,22,23 . Furthermore, we use image analysis to locate interdot charge transitions and automatically perform measurements of the interdot tunnel coupling 24 . Using simple feedback protocols, we demonstrate simultaneous tune-up of the i...

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Jellybean Quantum Dots in Silicon for Qubit Coupling and On‐Chip Quantum Chemistry

et al. 2023

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The small size and excellent integrability of silicon metal–oxide–semiconductor (SiMOS) quantum dot spin qubits make them an attractive system for mass‐manufacturable, scaled‐up quantum processors. Furthermore, classical control electronics can be integrated on‐chip, in‐between the qubits, if an architecture with sparse arrays of qubits is chosen. In such an architecture qubits are either transported across the chip via shuttling or coupled via mediating quantum systems over short‐to‐intermediate distances. This paper investigates the charge and spin characteristics of an elongated quantum dot—a so‐called jellybean quantum dot—for the prospects of acting as a qubit–qubit coupler. Charge transport, charge sensing, and magneto‐spectroscopy measurements are performed on a SiMOS quantum dot device at mK temperature and compared to Hartree–Fock multi‐electron simulations. At low electron occupancies where disorder effects and strong electron–electron interaction dominate over the electrostatic confinement potential, the data reveals the formation of three coupled dots, akin to a tunable, artificial molecule. One dot is formed centrally under the gate and two are formed at the edges. At high electron occupancies, these dots merge into one large dot with well‐defined spin states, verifying that jellybean dots have the potential to be used as qubit couplers in future quantum computing architectures.

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Site-Selective Quantum Control in an Isotopically Enriched Si28/Si0.7Ge0.3 Quadruple Quantum Dot

Cited by 72 publications

References 49 publications

Coherent transfer of quantum information in a silicon double quantum dot using resonant SWAP gates

Coherent transfer of quantum information in a silicon double quantum dot using resonant SWAP gates

Computer-automated tuning procedures for semiconductor quantum dot arrays

Jellybean Quantum Dots in Silicon for Qubit Coupling and On‐Chip Quantum Chemistry

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