Fast pulse sequences for dynamically corrected gates in singlet-triplet qubits

Abstract

We present a set of experimentally feasible pulse sequences that implement any single-qubit gate on a singlet-triplet spin qubit and demonstrate that these new sequences are up to three times faster than existing sequences in the literature. We show that these sequences can be extended to incorporate built-in dynamical error correction, yielding gates that are robust to both charge and magnetic field noise and up to twice as fast as previous dynamically corrected gate schemes. We present a thorough comparison of the performance of our new sequences with that of several existing ones using randomized benchmarking, considering both quasistatic and 1/f α noise models. We provide our results both as a function of evolution time and as a function of the number of gates, which respectively yield both an effective coherence time and an estimate of the number of gates that can be performed within this coherence time. We determine which set of pulse sequences gives the best results for a wide range of noise strengths and power spectra. Overall, we find that the traditional, slower sequences perform best when there is no field noise or when the noise contains significant high-frequency components; otherwise, our new, fast sequences exhibit the best performance.

Crosstalk error correction through dynamical decoupling of single-qubit gates in capacitively coupled singlet-triplet semiconductor spin qubits

“…While this is often a good approximation 19 , the noise in actual experimental systems is known to follow a power-law spectrum 16,53 (1/f α ). We see, however, from the previous work 44,45 that, even in this scenario, similar approaches to that which we adopt here to combat the effects of noise still result in noticeable improvement in gate fidelities. We thus expect similar results for the capacitively-coupled qubits considered here.…”

“…Three papers have been written using the supcode technique, one for the case in which only (electrical) charge noise is present 43 and two others in which (magnetic) field noise is also included 44,45 . This method, which we will be employing a generalization of in this work, consists of inserting an uncorrected "identity" operation into the pulse sequence for a given gate that is arranged in such a way as to cancel the noise-induced error to leading order.…”

“…(We refer to Ref. 45 for the necessary technical details here.) In principle, these degrees of freedom could be added to the list of free parameters j i , φ i in the uncorrected identity operation, possibly resulting in a marginally more optimal pulse sequence.…”

Implementation of Geometric Quantum Gates on Microwave‐Driven Semiconductor Charge Qubits

“…Several theoretical approaches have been proposed to mitigate the noise effects and improve the gate fidelities, including, for example, pulse engineering [ 18 ] and dynamically corrected gates. [ 19–23 ] Recently, it has been demonstrated that strongly microwave‐driven operations near the detuning sweet spots can effectively suppress the charge noises. [ 10,12,24–27 ] Despite these progresses, experimental gate fidelities are still below 90% [ 10 ] owing to the residual charge noise.…”

Dephasing of Exchange‐Coupled Spins in Quantum Dots for Quantum Computing

“…[ 41 ] It is important to understand the underlying decoherence mechanisms to further extend the coherence time of a qubit for high‐fidelity quantum gates. [ 42–50 ] Other aspects that are as important as decoherence are to increase the single‐spin gate speed through electric dipole spin resonance (EDSR), [ 51–61 ] improve robustness against noise through quantum control sequences or qubit encoding, [ 62–83 ] and design qubits for better scalability. [ 34–38,84–89 ] There are also theoretical studies of the quantum error correction scheme to suppress errors of spin qubits.…”