Seminar: Converting quantum circuits to graph states for photonic one-way computing

ABSTRACT

The lack of deterministic entangling gates, by means of only linear optics, makes the standard gate-based model of photonic quantum computing impractical. Therein, two-qubit gates are probabilistic and require the use of additional ancilla photons and post-selection. The one-way model of quantum computation, on the other hand, offers an alternative to universal quantum computing with linear optics. There, a highly entangled multiphoton state is used as a resource, from which single qubit measurements perform computation in a deterministic manner.

Proof-of-concept implementations of quantum algorithms using the one-way model and photonic setups have been demonstrated in the past. However, to enable circuit-level programming for optical one-way computers, arbitrary quantum circuits must be translated from the gate-based model to the one-way model and optimized according to the available resources. This is where the recently developed ZX-Calculus comes in handy, as it provides a graphical representation for quantum computations as well as a set of rules for optimization.

In the main part of this talk, I will give an overview of the different quantum computing schemes with single photons and describe our method for transforming arbitrary quantum circuits into an optimized measurement pattern and the underlying graph state. In particular, I will show how we can convert an arbitrary QASM input into a graphical representation that can be optimized using graph-theoretic transformation rules from ZX-Calculus before being translated into hardware instructions for an optical one-way processor.

In addition, I will highlight experimental progress and briefly report on our recent demonstration of polarization-encoded heralded three-photon Greenberger-Horne-Zeilinger states, which are an important building block for the scalable generation of large entangled multiphoton states.

BIOGRAPHY

Felix Zilk, M.Sc., is currently a PhD student at the Institute of Information Systems at the Vienna University of Technology (TU Wien). His main research interest is the application of photonic systems for quantum computing and the development of solutions for their integration with classical computing and HPC systems. Felix Zilk holds a master’s degree in physics from the University of Vienna. Before joining TU Wien, he was a research assistant at the Christian Doppler Laboratory for Photonic Quantum Computing, where he studied measurement-based quantum computing protocols and their software frameworks, particularly in experimental setups with photonic qubits. In parallel to his work at TU Wien, he is also a solutions architect for quantum computing at QMware.