Fast long-distance control of spin qubits by photon-assisted cotunneling

Stano, Peter; Klinovaja, Jelena; Braakman, Floris; Vandersypen, L. M. K.; Loss, Daniel

doi:10.1103/physrevb.92.075302

Cited by 21 publications

(24 citation statements)

References 69 publications

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“…Many of these mechanisms have in common that they allow the separation of the qubits by larger distances, varying from roughly one µm to roughly one mm. Proposals for coupling spin qubits at a distance rely on the use of superconducting resonators [16,19,27,30], capacitive coupling [24,25,37], ferromagnets [29], superconductors [28,32], intermediate dots or dot arrays [20,21,34,35,40], or surface acoustic wave cavities [31]. An alternative approach consists of shuttling electrons across the chip between distant quantum dots, where the electrons are propelled by time-varying gate voltages [17,36] or surface acoustic waves [22,23].…”

Section: Sparse Qubit Arrays and Local Electronicsmentioning

confidence: 99%

Interfacing spin qubits in quantum dots and donors—hot, dense, and coherent

et al. 2017

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Semiconductor spins are one of the few qubit realizations that remain a serious candidate for the implementation of large-scale quantum circuits. Excellent scalability is often argued for spin qubits defined by lithography and controlled via electrical signals, based on the success of conventional semiconductor integrated circuits. However, the wiring and interconnect requirements for quantum circuits are completely different from those for classical circuits, as individual direct current, pulsed and in some cases microwave control signals need to be routed from external sources to every qubit. This is further complicated by the requirement that these spin qubits currently operate at temperatures below 100 mK. Here, we review several strategies that are considered to address this crucial challenge in scaling quantum circuits based on electron spin qubits. Key assets of spin qubits include the potential to operate at 1 to 4 K, the high density of quantum dots or donors combined with possibilities to space them apart as needed, the extremely long-spin coherence times, and the rich options for integration with classical electronics based on the same technology.npj Quantum Information (2017) 3:34 ; doi:10.1038/s41534-017-0038-y INTRODUCTIONThe quantum devices in which quantum bits are stored and processed will form the lowest layer of a complex multi-layer system. 1-3 The system also includes classical electronics to measure and control the qubits, and a conventional computer to control and program these electronics. Increasingly, some of the important challenges involved in these intermediate layers and how they interact have become clear, and there is a strong need for forming a picture of how these challenges can be addressed.Focusing on the interface between the two lowest layers of a quantum computer, each of the quantum bits must receive a long sequence of externally generated control signals that translate to the steps in the computation. Furthermore, given the fragile nature of quantum states, large numbers of quantum bits must be read out periodically to check whether errors occurred along the way, and to correct them. 4 Such error correction is possible provided the probability of error per operation is below the accuracy threshold, which is around 1% for the so-called surface code, a scheme which can be operated on two-dimensional (2D) qubit arrays with nearest-neighbor couplings. 5,6 The read-out data must be processed rapidly and fed back to the qubits in the form of control signals. Since each qubit must separately interface with the outside world, the classical control system must scale along with the number of qubits, and so must the interface between qubits and classical control.The estimated number of physical qubits required for solving relevant problems in quantum chemistry or code breaking is in the 10 6 -10 8 range, using currently known quantum algorithms and quantum error correction methods. 7,8 For comparison, state-

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Section: Sparse Qubit Arrays and Local Electronicsmentioning

confidence: 99%

Interfacing spin qubits in quantum dots and donors—hot, dense, and coherent

et al. 2017

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“…Since the exchange interaction is limited to adjacent QDs, other long-range interactions have to be considered to overcome this technical difficulty allowing for a two-dimensional array of qubits which are spatially separated [236]. There are several proposals for the achievement of such an interaction, e.g., tunneling mediated by a superconductor [237,238], coupling though surface acoustic waves [239,240,241,242,243,244], ferromagnets [245], superexchange mediated by an additional QD [246,247,92,248], spatial adiabatic passage [249,222,250], photon assisted tunneling [251,252,253], and quantum Hall edge states [254,243]. The most practical ideas (up to date) seem to be Coulomb-based dipoledipole coupling [10,255,256] and cavity quantum electrodynamics (cQED) mediated coupling [137,16,187,211,105,17,257,258,106] which both use the electric dipole moment of the qubit, whereas in the second approach the interaction range is elongated by the use of a cavity as a mediator [97,98,16,17,3].…”

Section: Long-ranged Two-qubit Gatesmentioning

confidence: 99%

Three-electron spin qubits

Russ

Burkard

2017

J. Phys.: Condens. Matter

104

117

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The goal of this article is to review the progress of three-electron spin qubits from their inception to the state of the art. We direct the main focus towards the exchange-only qubit (Bacon et al 2000 Phys. Rev. Lett. 85 1758-61, DiVincenzo et al 2000 Nature 408 339) and its derived versions, e.g. the resonant exchange (RX) qubit, but we also discuss other qubit implementations using three electron spins. For each three-spin qubit we describe the qubit model, the envisioned physical realization, the implementations of single-qubit operations, as well as the read-out and initialization schemes. Two-qubit gates and decoherence properties are discussed for the RX qubit and the exchange-only qubit, thereby completing the list of requirements for quantum computation for a viable candidate qubit implementation. We start by describing the full system of three electrons in a triple quantum dot, then discuss the charge-stability diagram, restricting ourselves to the relevant subsystem, introduce the qubit states, and discuss important transitions to other charge states (Russ et al 2016 Phys. Rev. B 94 165411). Introducing the various qubit implementations, we begin with the exchange-only qubit (DiVincenzo et al 2000 Nature 408 339, Laird et al 2010 Phys. Rev. B 82 075403), followed by the RX qubit (Medford et al 2013 Phys. Rev. Lett. 111 050501, Taylor et al 2013 Phys. Rev. Lett. 111 050502), the spin-charge qubit (Kyriakidis and Burkard 2007 Phys. Rev. B 75 115324), and the hybrid qubit (Shi et al 2012 Phys. Rev. Lett. 108 140503, Koh et al 2012 Phys. Rev. Lett. 109 250503, Cao et al 2016 Phys. Rev. Lett. 116 086801, Thorgrimsson et al 2016 arXiv:1611.04945). The main focus will be on the exchange-only qubit and its modification, the RX qubit, whose single-qubit operations are realized by driving the qubit at its resonant frequency in the microwave range similar to electron spin resonance. Two different types of two-qubit operations are presented for the exchange-only qubits which can be divided into short-ranged and long-ranged interactions. Both of these interaction types are expected to be necessary in a large-scale quantum computer. The short-ranged interactions use the exchange coupling by placing qubits next to each other and applying exchange-pulses (DiVincenzo et al 2000 Nature 408 339, Fong and Wandzura 2011 Quantum Inf. Comput. 11 1003, Setiawan et al 2014 Phys. Rev. B 89 085314, Zeuch et al 2014 Phys. Rev. B 90 045306, Doherty and Wardrop 2013 Phys. Rev. Lett. 111 050503, Shim and Tahan 2016 Phys. Rev. B 93 121410), while the long-ranged interactions use the photons of a superconducting microwave cavity as a mediator in order to couple two qubits over long distances (Russ and Burkard 2015 Phys. Rev. B 92 205412, Srinivasa et al 2016 Phys. Rev. B 94 205421). The nature of the three-electron qubit states each having the same total spin and total spin in z-direction (same Zeeman energy) provides a natural protection against several sources of noise (DiVincenzo et al 2000 Nature 408 339, Taylor et al 2013 Phys. R...

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“…Driving at resonance across the band gap, that is with ℏω ¼ Δ g , opens a dynamical gap [87,88], essential for inducing nontrivial topology [52,57,89]. Using the Floquet representation [90][91][92], this gap arises as a splitting of degeneracies in the quasienergy spectrum of the Floquet operator. It corresponds to the lowest order of degenerate perturbation theory in the electric field amplitude, or, in another words, to a single photon emission or absorption process.…”

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confidence: 99%

Topological Floquet Phases in Driven Coupled Rashba Nanowires

2016

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We consider periodically driven arrays of weakly coupled wires with conduction and valence bands of Rashba type and study the resulting Floquet states. This nonequilibrium system can be tuned into nontrivial phases such as topological insulators, Weyl semimetals, and dispersionless zero-energy edge mode regimes. In the presence of strong electron-electron interactions, we generalize these regimes to the fractional case, where elementary excitations have fractional charges e=m with m being an odd integer. DOI: 10.1103/PhysRevLett.116.176401 Introduction.-Topological effects in condensed matter systems have attracted attention for many years. From the quantum Hall effect over topological insulators (TIs) [1][2][3][4][5][6][7][8][9][10][11][12] and Weyl semimetals [13][14][15][16][17], to Majorana fermions and parafermions [39][40][41][42][43][44][45][46][47][48][49], the interest is driven both by fundamental physics and the promise for topological quantum computation. Despite the many proposals for topological systems, the search for the most optimal material still continues unabated.While most studies were focused on static structures, it has recently been proposed to extend topological phases to nonequilibrium systems, described by Floquet states . Remarkably, this approach no longer relies on given material properties, such as strong spin orbit interactions (SOIs), typically necessary for reaching topological regimes, but instead allows one to turn initially nontopological materials such as graphene [50] and non-bandinverted semiconducting wells into TIs [52] by applying an external driving field.An even bigger challenge is to describe topological effects that involve fractional excitations. This requires the presence of strong electron-electron interactions. However, given the difficulties in the search for conventional TIs, it would be even more surprising to expect such phases to occur naturally. Moreover, even if they existed, twodimensional (2D) systems with electron-electron interactions are difficult to describe analytically and often progress can come only from numerics [61].Here, we circumvent this difficulty by considering strongly anisotropic 2D systems [71][72][73][74] formed by weakly coupled Rashba wires (see Fig. 1), where each of them can be treated as a one-dimensional Luttinger liquid by bosonization [75][76][77][78][79][80][81][82][83][84][85][86]. This will allow us to introduce the Floquet version not only of TIs but also of Weyl semimetals in driven 2D systems. Importantly, in this way we can also address fractional regimes and are able to obtain the Floquet version of fractional TIs and Weyl semimetals.

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Fast long-distance control of spin qubits by photon-assisted cotunneling

Cited by 21 publications

References 69 publications

Interfacing spin qubits in quantum dots and donors—hot, dense, and coherent

Interfacing spin qubits in quantum dots and donors—hot, dense, and coherent

Three-electron spin qubits

Topological Floquet Phases in Driven Coupled Rashba Nanowires

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