21 September 2023

A new spin on quantum computing with photons


New paper outlines a promising route to scalable quantum computing with quantum emitters and linear-optical elements.

two men on stairs
Stefano Paesani and Ben Brown photographed at NQCP

In a new article published in Physical Review Letters, Stefano Paesani, NQCP, and Ben Brown, IBM Quantum, propose a new efficient fault-tolerant quantum computing architecture based on measurements of photonic entangled states that are produced by spin-photon interfaces in deterministic single photon sources.

A quantum-computing architecture will only scale to run large algorithms if we can eliminate the errors the qubits experience due to system imperfections and random noise. To eliminate errors completely, it is essential to arrange the qubits in fault-tolerant architecture that can correct errors while the quantum information is processed.

A good architecture needs to exploit the positive characteristics of the underlying hardware platform. In this work Stefano Paesani and Ben Brown propose a quantum-computing architecture based on quantum emitters. A quantum emitter produces photonic qubits from a matter-based system such as quantum dots. The benefits of this approach are three-fold: long coherence times of flying photonic qubits, their high mobility and speed, and the control available at the matter level where the photons are deterministically produced. 

The proposal uses entangled chains of photonic qubits that can be generated from quantum emitters. Once these entangled chains are produced, their individual photonic qubits are measured in pairs, using 'fusion measurements,' to complete computations while simultaneously identifying and accounting for any errors that occur.

Given that these operations are now under development at NQCP and at the center for hybrid quantum networks (HyQ), it is reasonable to expect hardware to implement this architecture will be available in the near term. In addition, numerical simulations show that this architecture can tolerate high rates of noise. Therefore, the proposal demonstrates a promising path to realizing a photonic quantum computer in laboratories at the University of Copenhagen as well as other laboratories worldwide.

It is important to develop new theoretical frameworks for the different hardware platforms we have available to tackle the huge challenge of building a large scale quantum computer.

Ben Brown, Research Scientist, IBM Quantum

Photonic qubits are exciting as a platform because their high mobility and speed enable operations that are hard to achieve with other qubit types - requiring us to think about completely different ways to perform quantum computations.

Stefano Paesani, Assistant Professor, NQCP