Quantum Computing Takes A Step Forward With Quantum Data Bus

An illustration of applying perfect state transfer to one photon of an entangled pair, relocating it to a distant location while preserving the quantum information and entanglement.
(Image courtesy of RMIT University.)

For the first time, researchers have demonstrated an effective method for transferring quantum information from one location to another. This could pave the way towards a quantum data bus, an essential component for practical quantum computing.

Standard computer processors come equipped with data buses capable of transferring traditional bits of information, which is necessary for tasks such as communication between the CPU and memory. Building a practical quantum computer would require a similar capability for quantum bits. However, it is challenging to reliably transfer quantum information due to the fragile nature of quantum states.

Perfect State Transfer

The quantum bits were transferred with an implementation of the perfect state transfer (PST) protocol, which uses a one-dimensional lattice to connect two quantum processors. Through Hamiltonian evolution over a specific time, the quantum state in the initial lattice site is transferred to the final lattice site with 100% probability.

The evolution of a perfect state transfer lattice: the input state at the first site is transferred to the output state at the final site. (Image courtesy of the researchers and Nature Communications.)

While most research on PST has been strictly theoretical, the recent demonstration showed the preservation of the encoded quantum states with an average fidelity of 97.1%. An extension of standard PST, the demonstration was realized as an array of 11 evanescently-coupled waveguides using a polarization-encoded photon to store the quantum information.

Bits vs. Qubits

Quantum computing, as opposed to traditional computing, makes use of the strange properties of quantum mechanics to greatly increase processing capabilities. Traditional bits have the binary restriction of being either a 0 or 1. Quantum bits, or qubits, are not so constrained: they can exist as a superposition of both 0 and 1. This property can be harnessed to greatly reduce the computation time required for certain classes of problems.

"It could make the critical difference for discovering new drugs, developing a perfectly secure quantum Internet and even improving facial recognition,'' said Dr. Alberto Peruzzo, director of the Quantum Photonics Laboratory, which helped conduct the research. He believes his team’s results are “a breakthrough that has the potential to open up quantum computing in the near future."

The research paper can be found in Nature Communications.