Capacitively coupled singlet-triplet qubits in the double charge resonant regime

Abstract

We investigate a method for entangling two singlet-triplet qubits in adjacent double quantum dots via capacitive interactions. In contrast to prior work, here we focus on a regime with strong interactions between the qubits. The interplay of the interaction energy and simultaneous large detunings for both double dots gives rise to the double charge resonant regime, in which the unpolarized (1111) and fully polarized (0202) four-electron states in the absence of interqubit tunneling are near degeneracy, while being energetically well-separated from the partially polarized (0211 and 1102) states. A rapid controlled-phase gate may be realized by combining time evolution in this regime in the presence of intraqubit tunneling and the interqubit Coulomb interaction with refocusing $\pi$ pulses that swap the singly occupied singlet and triplet states of the two qubits via, e.g., magnetic gradients. We calculate the fidelity of this entangling gate, incorporating models for two types of noise -- charge fluctuations in the single-qubit detunings and charge relaxation within the low-energy subspace via electron-phonon interaction -- and identify parameter regimes that optimize the fidelity. The rates of phonon-induced decay for pairs of GaAs or Si double quantum dots vary with the sizes of the dipolar and quadrupolar contributions and are several orders of magnitude smaller for Si, leading to high theoretical gate fidelities for coupled singlet-triplet qubits in Si dots. We also consider the dependence of the capacitive coupling on the relative orientation of the double dots and find that a linear geometry provides the fastest potential gate.

14 pages, 7 figures (revised)

References in corpus (20)

• Electrically driven single electron spin resonance in a slanting Zeeman field
• Demonstration of Entanglement of Electrostatically Coupled Singlet-Triplet Qubits
• Prospects for Spin-Based Quantum Computing
• Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization
• Electrometry Using Coherent Exchange Oscillations in a Singlet-Triplet-Qubit
• Singlet-triplet decoherence due to nuclear spins in a double quantum dot
• Two-axis control of a singlet-triplet qubit with an integrated micromagnet
• Ultra-long distance interaction between spin qubits
• Universal set of quantum gates for double-dot spin qubits with fixed interdot coupling
• Experimental signature of phonon-mediated spin relaxation
• Noise-resistant control for a spin qubit array
• Conditional operation of a spin qubit
• Quantum gates between capacitively coupled double quantum dot two-spin qubits
• Exchange-based two-qubit gate for singlet-triplet qubits
• Two-Qubit Couplings of Singlet-Triplet Qubits Mediated by One Quantum State
• Directly accessible entangling gates for capacitively coupled singlet-triplet qubits
• Theory of Spin Relaxation in Two-Electron Lateral Coupled Si/SiGe Quantum Dots
• Improving the gate fidelity of capacitively coupled spin qubits
• Dynamics of spin-flip photon-assisted tunneling
• Spin Qubits in Multi-Electron Quantum Dots

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• Fault-Tolerant Quantum Computation for Singlet-Triplet Qubits with Leakage Errors
• Improving the gate fidelity of capacitively coupled spin qubits
• Paired electron motion in interacting chains of quantum dots
• Programmable two-qubit gates in capacitively coupled flopping-mode spin qubits
• Dynamics of two coupled semiconductor spin qubits in a noisy environment
• Probing two-qubit capacitive interactions beyond bilinear regime using dual Hamiltonian parameter estimations
• Charge noise suppression in capacitively coupled singlet-triplet spin qubits under magnetic field
• Simulation of Coupling Strength of Capacitively Coupled Singlet-Triplet Qubits
• Energy spectrum, exchange interaction and gate crosstalk in a pair of double-quantum-dot system: a molecular orbital calculation
• Robust entangling gate for capacitively coupled few-electron singlet-triplet qubits
• Two-qubit logical operations in three quantum dots system
• Two-qubit sweet spots for capacitively coupled exchange-only spin qubits