Researchers in Japan have made a groundbreaking discovery that could pave the way for the development of large-scale superconducting quantum computers. Their innovative superconducting circuit can control multiple qubits using a single cable, significantly increasing the number of controllable qubits and bringing us closer to practical quantum computing.
Solving the Challenge of Qubit Control
Quantum computers hold the potential to revolutionize fields from cryptography research to experimental science. However, a major practical roadblock to large-scale quantum computing has been the challenge of controlling many qubits.
Instead of transferring an individual microwave signal to every qubit separately via separate cables as is done with conventional quantum computers, something that in practice quickly becomes problematic with a large number of qubits. The latter is true because scaling up a quantum computer runs into an inescapable limit that the number of controllable qubits does not exceed 1,000.
Microwave Multiplexing: The Scalable Instrument for Qubit Control
The team’s novel superconducting circuit employs a method called microwave multiplexing, which makes it possible to control numerous qubits via a single cable. Now, rather than using a coaxial cable for each qubit, the new architecture enables multiple microwave signals (each packed with the control signals it takes to manipulate the qubit) onto a single circuit.
However, if successful it could increase the number of microwave signals on a single cable by about 1,000 times and hence provide control for many more qubits than previously possible. In a proof-of-concept experiment at liquid-helium temperatures (4.2 K), the researchers verified that this superconducting circuit works.
This discovery allowed scientists to reach the million-plus-qubit, general-purpose quantum computer upper limit they set for themselves. This degree of scalability is essential for realizing the true potential of quantum computing, including the ability to solve difficult problems that are currently impossible for classical computers to tackle.
Conclusion
This work on a new superconducting circuit that uses this method to control qubits will be an important milestone in the journey toward functioning, large-scale quantum computers. This breakthrough overcomes a major bottleneck in quantum computing by enabling the control of thousands of qubits with just one cable, and takes us closer to realising the transformative potential of this technology. As research continues, we can expect many additional exciting developments to come that will define the future of computing and scientific discovery.
