Researchers at Toshiba Corporation and RIKEN have made a breakthrough in quantum computing, developing a tunable coupler that can connect two superconducting qubits with unprecedented precision. This innovation enables the switching between executing and halting operations by turning the coupling between qubits “on” or “off”.
The team, led by Yasunobu Nakamura, has achieved a two-qubit gate fidelity of 98.4%, paving the way for developing practical quantum computers. The coupler’s performance can be tuned by adjusting an external magnetic flux, allowing for a wide range of coupling strengths from 6 kHz to 80 MHz. This technology can potentially suppress crosstalk errors, which occur when control electromagnetic waves applied to one qubit affect another.
Toshiba and RIKEN aim to enhance the performance of their double-transmon coupler further, targeting a two-qubit gate fidelity of 99.99% and scaling up the system for practical applications.
Toshiba Corporation and RIKEN researchers have made significant progress in developing a tunable coupler that can connect two fixed-frequency transmon qubits. This device allows for the switching between executing and halting operations by turning the coupling between qubits “on” or “off.” The key innovation here is the ability to tune the coupling strength over a wide range, from 6 kHz to 80 MHz, by adjusting the external magnetic flux within the loop.
This achievement is crucial because conventional tunable couplers struggle to turn off the coupling completely when there’s a significant frequency difference between two qubits. This residual coupling leads to errors caused by crosstalk, which can be detrimental to the quantum computer’s overall performance.
The double-transmon coupler design comprises two fixed-frequency transmon qubits and a Josephson junction (JJ) area. The optical microscope image in Figure 2 shows the fabricated circuit, with a close-up of the JJ area. By adjusting the external magnetic flux, the researchers can tune the coupling strength to achieve high-fidelity two-qubit gate operations.
The measurement results in demonstrate this coupler’s impressive performance, with a two-qubit gate fidelity of up to 98.5%. This is a significant milestone towards realizing practical quantum computers.
Looking ahead, the research team aims to further enhance the double-transmon coupler’s performance, targeting a two-qubit gate fidelity of 99.99%. They will also develop technologies to scale up the system while maintaining its high performance.
This research was partially supported by the Ministry of Education, Culture, Sports, Science and Technology’s Quantum Leap Flagship Program (Q-LEAP), highlighting the importance of government funding in driving innovation in quantum computing.
In conclusion, this breakthrough in double-transmon coupler design brings us closer to realizing practical superconducting quantum computers. As a science journalist, I’m excited to see how this technology will continue to evolve and shape the future of quantum computing.
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