The Quantum Volume of qubit systems must at least double annually to beat classical computing with a working quantum computer in the next ten years, IBM says.
IBM uses Quantum Volume as an indication of the performance of a quantum computer, as an alternative to simply the number of qubits in a system. It concerns a measurement on the largest quantum circuit with the same width and depth of quantum systems, where the result says something about the margin of error. The more uncontrolled interactions within the system, the lower the Quantum Volume and vice versa.
The measurement method has been applied by IBM to its various quantum processors. For example, the system codenamed Tenerife from 2017 with five qubits has a Quantum Volume of four, the Tokyo from 2018 with twenty qubits has a volume of eight and this year’s IBM Q Systems One, also with twenty qubits, has a Quantum Volume of sixteen.
The method is intended for so-called nisq systems, which stands for noisy intermediate-scale quantum. These are quantum systems of the present and the near future, which will not yet cause a revolution in computing, but will usher in the era in which quantum computers will become more powerful than the fastest classical computers.
In order to reach this moment of quantum advantage, also called quantum supremacy, in the next ten years, the annual doubling of the quantum volume must continue, argues IBM, making a comparison with the famous Moore’s Law. According to IBM, a significant performance improvement over traditional computing occurs when a computation is performed hundreds or thousands of times faster, requires a fraction of the amount of RAM, or produces a result that could never have been achieved using a conventional computer.
IBM also ran benchmarks at the qubit level, among other things to determine the error margin of a single qubit and that of a controlled not-gate of two qubits. This also showed that the properties of the IBM Q System One have been significantly improved compared to the first generation of systems. IBM will make new, higher-performance quantum systems available in the second half of 2019, at the opening of its new quantum computing center in New York State.