One of the primary uses envisioned for a quantum computer is the execution of Shor's algorithm. This is a tool that can factor larger numbers with great speed, but can only be run on a quantum computer. As those computers are still in their infancy, so are their attempts at running Shor's algorithm by only factoring 15, the smallest compound number it will work on. Researchers at the University of Bristol however have factored the next largest value and done so with fewer photons.
Part of the reason Shor's algorithm is so hard to run on values larger than 15 is creating qubits for the computation to use. The researchers got around that issue though by recycling the photons they used. To accomplish this, the researchers first had to identify places the algorithm could be separated, so the photons used for one part could be recycled for another. This enabled them to factor the number 21 with Shor's algorithm, and while that may not seem impressive, it does represent a new record.
This ability to recycle particles could become instrumental to future quantum computers. By reducing the number of individual qubits required for operation, the overall complexity of the computer could drop considerably, without sacrificing capability.