Pulse sequence designed for robust 
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-phase gates in SiMOS and Si/SiGe double quantum dots

Güngördü, Utkan; Kestner, J. P.

doi:10.1103/physrevb.98.165301

Cited by 25 publications

(44 citation statements)

References 47 publications

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“…We point out that this technique can also be applied to heavy-hole systems, where the control of the hole spin via the tunneling and strong SOC has been demonstrated for silicon-based DQDs [34]. Recent publications presenting theoretical proposals for DQD with strong SOC [19,20] and transverse magnetic field [35] are potentially consistent with our method and can be compared to other protocols based on the approach proposed here. Finally, a similar approach can be used to design the spin and mass transport of cold atoms in optically produced potentials [36].…”

Section: Discussionsupporting

confidence: 59%

Qubit gates with simultaneous transport in double quantum dots

Chen

Muga

et al. 2018

New J. Phys.

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A single electron spin in a double quantum dot in a magnetic field is considered in terms of a four-level system. By describing the electron motion between the potential minima via spin-conserving tunneling and spin flip caused by a spin-orbit coupling, we inversely engineer faster-than-adiabatic state manipulation operations based on the geometry of four-dimensional rotations. In particular, we show how to transport a qubit among the quantum dots performing simultaneously required spin rotations. IntroductionDevice architecture based on electrons confined in coupled quantum dots [1-4] is considered as a potential and significant candidate for quantum computing and quantum information processing. The advantages of this architecture rely on the facts that electron spin is a natural qubit with spin-up and spin-down states, mature semiconductor technology may be used, and long coherence times on the scale of microseconds have been achieved in these systems [5,6]. Laboratories use electric, microwave or magnetic fields to manipulate spin states, performing 10 3 -10 5 operations in the spin dephasing time [5-10].Scalability of quantum information devices is a major challenge for any architecture, and it is associated with the capability to transport qubits. In this paper we theoretically explore a four-level model for a spin in a double quantum dot (DQD) aiming at the possibilities to implement fast qubit transport with simultaneous qubit rotations. We achieve this goal for arbitrary rotations by controlling the synchronized time dependences of interdot tunneling and spin-orbit coupling (SOC). We inverse-engineer these time dependences based on our recent work [11] on the control of four-level systems. The method separates population control from control of the phases of the bare state basis [12]. Populations can be mapped onto a four-dimensional (4D) sphere such that their evolution amounts to 4D transformation controlled by the (4D-)rotation Hamiltonian that may be engineered from the target state (in our case via isoclinic rotations and quaternions). A full Hamiltonian can then be constructed from the rotation Hamiltonian to realize the desired phase changes. Arbitrary state manipulations require full flexibility in the Hamiltonian, i.e. the possibility to implement the different Hamiltonian matrix elements with specific time-dependences. In the systems of interest, however, there are constraints that hinder certain manipulations and transitions. In particular, in this paper we examine the Hamiltonian structure that corresponds to combined tunneling and SOC controllable couplings, and deduce the possible transformations.Spin-orbit coupling in semiconductors consists of two main contributions due to the Dresselhaus-and the Bychkov-Rashba-effect. The former is due to the bulk inversion asymmetry of the material and the latter results from the structure inversion asymmetry, produced, e.g. by the confining potential or an external electric field [13]. The practical advantage of the Rashba coupling is the ability to man...

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Section: Discussionsupporting

confidence: 59%

Qubit gates with simultaneous transport in double quantum dots

Chen

Muga

et al. 2018

New J. Phys.

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“…Assuming further a constant distribution of activation energies, P(E, T ) = const and inserting this into Eq. 13 the characteristic 1/f noise with a linear temperature dependence can be reproduced [28],…”

Section: Temperature Dependence Of the Dephasing Timesmentioning

confidence: 95%

Universal quantum logic in hot silicon qubits

Petit

Eenink

Russ

et al. 2020

Nature

289

233

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Quantum computation requires many qubits that can be coherently controlled and coupled to each other [1]. Qubits that are defined using lithographic techniques are often argued to be promising platforms for scalability, since they can be implemented using semiconductor fabrication technology [2][3][4][5]. However, leading solidstate approaches function only at temperatures below 100 mK, where cooling power is extremely limited, and this severely impacts the perspective for practical quantum computation. Recent works on spins in silicon have shown steps towards a platform that can be operated at higher temperatures by demonstrating long spin lifetimes [6], gate-based spin readout [7], and coherent singlespin control [8], but the crucial two-qubit logic gate has been missing. Here we demonstrate that silicon quantum dots can have sufficient thermal robustness to enable the execution of a universal gate set above one Kelvin. We obtain singlequbit control via electron-spin-resonance (ESR) and readout using Pauli spin blockade. We show individual coherent control of two qubits and measure single-qubit fidelities up to 99.3 %. We demonstrate tunability of the exchange interaction between the two spins from 0.5 up to 18 MHz and use this to execute coherent two-qubit controlled rotations (CROT). The demonstration of 'hot' and universal quantum logic in a semiconductor platform paves the way for quantum integrated circuits hosting the quantum hardware and their control circuitry all on the same chip, providing a scalable approach towards practical quantum information.Spin qubits based on quantum dots are among the most promising candidates for large-scale quantum computation [2,9,10]. Quantum coherence can be maintained in these systems for extremely long times [11] by using isotopically enriched silicon ( 28 Si) as the host material [12]. This has enabled the demonstration of singlequbit control with fidelities exceeding 99.9% [13,14] and the execution of two-qubit logic [15][16][17][18]. The potential to build larger systems with quantum dots manifests in the ability to deterministically engineer and optimize qubit locations and interactions using a technology that greatly resembles today's complementary metal-oxide semiconductor (CMOS) manufacturing. Nonetheless, quantum error correction schemes predict that millions to billions of qubits will be needed for practical quantum informa-tion [19]. Considering that today's devices make use of more than one terminal per qubit [20], wiring up such large systems remains a formidable task. In order to avoid an interconnect bottleneck, quantum integrated circuits hosting the qubits and their electronic control on the same chip have been proposed [2,3,21]. While these architectures provide an elegant way to increase the qubit count to large numbers by leveraging the success of classical integrated circuits, a key question is whether the qubits will be robust against the thermal noise imposed by the power dissipation of the electronics. Demonstrating a universal gate set at elevat...

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“…To improve the fidelity and robustness of these threequbit gates, it may be advantageous to employ dynamically corrected gates [46]. Provided the noise dynamics are slow compared to the gate times, such methods can lead to substantial improvements in the gate fidelities and robustness of the gates to calibration errors [6,47,48].…”

Section: Outlook and Conclusionmentioning

confidence: 99%

Protocol for a resonantly driven three-qubit Toffoli gate with silicon spin qubits

Gullans

Petta

2019

Phys. Rev. B

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The three-qubit Toffoli gate plays an important role in quantum error correction and complex quantum algorithms such as Shor's factoring algorithm, motivating the search for efficient implementations of this gate. Here we introduce a Toffoli gate suitable for exchange-coupled electron spin qubits in silicon quantum dot arrays. Our protocol is a natural extension of a previously demonstrated resonantly driven CNOT gate for silicon spin qubits. It is based on a single exchange pulse combined with a resonant microwave drive, with an operation time on the order of 100 ns and fidelity exceeding 99%. We analyze the impact of calibration errors and 1/f noise on the gate fidelity and compare the gate performance to Toffoli gates synthesized from two-qubit gates. Our approach is readily generalized to other controlled three-qubit gates such as the Deutsch and Fredkin gates.

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Pulse sequence designed for robust C -phase gates in SiMOS and Si/SiGe double quantum dots

Cited by 25 publications

References 47 publications

Qubit gates with simultaneous transport in double quantum dots

Qubit gates with simultaneous transport in double quantum dots

Universal quantum logic in hot silicon qubits

Protocol for a resonantly driven three-qubit Toffoli gate with silicon spin qubits

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