Researchers from the RIKEN Center for Quantum Computing and Toshiba have developed a quantum computer gate using a double-transmon coupler (DTC), significantly improving the quantum gates’ fidelity.
They achieved a 99.92% fidelity for a two-qubit CZ gate and 99.98% for a single-qubit gate. This advancement, part of the Q-LEAP project, enhances the performance of current noisy intermediate-scale quantum (NISQ) devices and moves closer to fault-tolerant quantum computation with effective error correction.
The DTC, a new tunable coupler, addresses challenges in connecting qubits with high fidelity, suppressing noise, and enabling rapid, high-fidelity gate operations even with detuned qubits.
A key aspect of the current work is using reinforcement learning to construct a quantum gate with state-of-the-art fabrication techniques. This machine learning approach allowed the researchers to translate the theoretical potential of the double-transmon coupler (DTC) into a practical application. By optimizing the balance between two error types—leakage and decoherence errors—they determined an optimal gate length of 48 nanoseconds, achieving among the highest fidelity levels reported in the field.
Yasunobu Nakamura, director of the RIKEN Center for Quantum Computing, said, “By reducing the error rates in quantum gates, we have made more reliable and accurate quantum computations possible. This is particularly important for developing fault-tolerant quantum computers, which are the future of quantum computing.”
He continues, “This device’s ability to perform effectively with highly detuned qubits makes it a versatile and competitive building block for various quantum computing architectures. This adaptability ensures that it can be integrated into existing and future superconducting quantum processors, enhancing their overall performance and scalability. We plan to try to achieve a shorter gate length in the future, as this could help minimize the incoherent error.”
Journal Reference:
- Rui Li, Kentaro Kubo, Yinghao Ho, Zhiguang Yan et al. Realization of High-Fidelity CZ Gate Based on a Double-Transmon Coupler. Physical Review X. DOI: 10.1103/PhysRevX.14.041050
