Flopping-mode electric dipole spin resonance

Abstract

Traditional approaches to controlling single spins in quantum dots require the generation of large electromagnetic fields to drive many Rabi oscillations within the spin coherence time. We demonstrate "flopping-mode" electric dipole spin resonance, where an electron is electrically driven in a Si/SiGe double quantum dot in the presence of a large magnetic field gradient. At zero detuning, charge delocalization across the double quantum dot enhances coupling to the drive field and enables low power electric dipole spin resonance. Through dispersive measurements of the single electron spin state, we demonstrate a nearly three order of magnitude improvement in driving efficiency using flopping-mode resonance, which should facilitate low power spin control in quantum dot arrays.Recent advances in silicon spin qubits have bolstered their standing as a platform for scalable quantum information processing. As single-qubit gate fidelities exceed 99.9% [1], two-qubit gate fidelities improve [2][3][4][5][6], and the field accelerates towards large multi-qubit arrays [7,8], developing the tools necessary for efficient and scalable spin control is critical [9]. While it is possible to implement single electron spin resonance in quantum dots (QDs) using ac magnetic fields [10], the requisite high drive powers and associated heat loads are technically challenging and place limitations on attainable Rabi frequencies [11]. As spin systems are scaled beyond a few qubits, methods of spin control which minimize dissipation and reduce qubit crosstalk will be important for low temperature quantum information processing [12].Electric dipole spin resonance (EDSR) is an alternative to conventional electron spin resonance. In EDSR, static gradient magnetic fields and oscillating electric fields are used to drive spin rotations [13]. The origin of the effective magnetic field gradient varies across implementations: intrinsic spin-orbit coupling [14][15][16], hyperfine coupling [17], and g-factor modulation [18] have been used to couple electric fields to spin states. The inhomogeneous magnetic field generated by a micromagnet [19,20] has been used to create a synthetic spin-orbit field for EDSR, enabling high fidelity control [1]. Conveniently, this magnetic field gradient gives rise to a spatially varying Zeeman splitting, enabling spins in neighboring QDs to be selectively addressed [11,19,[21][22][23][24][25].In this Letter, we demonstrate a novel mechanism for driving low-power, coherent spin rotations, which we call "flopping-mode EDSR". In conventional EDSR, the electric drive field couples to a charge trapped in a single quantum dot, leading to a relatively small electronic displacement [16]. We instead drive single spin rotations in a DQD close to zero detuning, = 0, where the electric field can force the electron to flop back and forth between the left and right dots, thereby sampling a larger variation in transverse magnetic field. We call this configuration the "flopping-mode".Neglecting spin, the Hamiltonian describing a singl...

Fast spin-valley-based quantum gates in Si with micromagnets

“…Thus, one can electrically tune the valley splitting to turn on the SVM for spin manipulation and spin-spin coupling, and turn off the SVM for the idling qubits. Furthermore, with the SVM boosted EDSR in a single QD instead of a double QD 22,25,28,29,82 , a spin qubit-based architecture could be simplified without sacrificing manipulation speed and tunability.…”

Electric-field control and noise protection of the flopping-mode spin qubit

“…This expression should be viewed as an approximate interpolation between the limiting cases where relaxation rate γ 1,s or the low-frequency noise are dominating [50]. Increasing the detuning localizes the electron more in a single QD and the flopping-mode EDSR mechanism described above may compete with other EDSR mechanisms that take place in a SQD, via excited orbital or valley states [23,27,[51][52][53][54][55][56].…”

“…The micromagnet could be designed to induce a longitudinal magnetic field gradient between the left and the right QDs with the aim of obtaining a different spin resonance frequency depending on the electron position. Fabrication misalignments can also give rise to both longitudinal gradients and overall transverse magnetic fields [16,50,60], i.e., the magnetic field components in the right and left QD positions may be B…”

“…where E orb is the orbital energy, E orb ≈ 1 − 3 meV, and m * e is the electron effective mass. Since the drive power is proportional to the square of the electric field, P ∝ E 2 ac , the power necessary to drive the spin qubit at a given Rabi frequency follows [50]…”

Programable two-qubit gates in capacitively coupled flopping-mode spin qubits

“…Motivated by recent experimental work on capacitive coupling between QD qubits [13,16,17,31,32] and in QD arrays with different spatial configurations [33][34][35][36][37], we consider here the capacitive coupling between flopping-mode spin qubits [38][39][40][41] and investigate the realization of two-qubit gates. As shown in Fig.…”