Composite two-qubit quantum gates

Bettina Just

Ming Ni, Rong-Long Ma, Zhenzhen Kong +11 more

On the path toward large-scale quantum information processing, the ability to implement diverse types of two-qubit gates is preferable for device structure designs and quantum circuit compilations. Here, taking advantage of the inherent Heisenberg interaction between spin qubits, we propose and verify a fast composite two-qubit gate scheme for spin qubits based on semiconductor quantum dots. Theoretical results indicate that the gate scheme facilitates the simultaneous implementation of various types of two-qubit gates, including five types of essential two-qubit gates, iswap-family gates, and fermionic simulation gates. Furthermore, we observe an excellent match between the measured and simulated results, representing the preliminary experimental demonstration of the composite gate scheme. We believe that, with this versatile composite two-qubit gate scheme, the available broad-spectrum two-qubit operations will allow us to efficiently utilize the hardware resources and accelerate the advancement of noisy intermediate-scale quantum computing.

Boyan T. Torosov, Nikolay V. Vitanov

We propose a method to construct composite two-qubit gates with narrowband profiles with respect to the spin-spin coupling. The composite sequences are selective to the variations in the amplitude and duration of the spin-spin coupling, and can be used for highly selective qubit addressing with greatly reduced crosstalk, quantum logic spectroscopy, and quantum sensing.

Yang-Yang Yu, Guang-Hui Zhang, Yan-Jie He +3 more

We propose a universal approach based on Hamiltonian inverse engineering to realize a set of parameterized two-qubit gates. This method possesses unique advantages to simultaneous control of transitions among four energy levels, providing a simpler and effective way to construct composite two-qubit gates with fewer operations than traditional methods. Applied to silicon double quantum dots (DQDs), one can realize a one-step fSim gate and a B gate with only one pulse switch. Of note, the method can be further integrated with various optimization theories to enhance gate performance. Based on quantum optimal control theory, we develop a high-fidelity fSim gate scheme with experimentally feasible pulse shapes, featuring an average gate time of 50 ns and a theoretical fidelity of 99.95% in the presence of decoherence and approximation error. By incorporating geometric quantum gate principles, we propose a combined geometric and dynamic fSim gate scheme. Numerical simulations demonstrate that this hybrid scheme exhibits stronger robustness against systematic errors compared to the purely dynamic approach. Our method is generalizable to arbitrary two-qubit physical systems, offering a feasible pathway for rapidly and robustly constructing composite two-qubit gates.

Masamitsu Bando, Tsubasa Ichikawa, Yasushi Kondo +1 more

Christopher J. Ballance