A Blueprint for Photonic Quantum Computer

Recent technological advances allow to build revolutionary devices for information processing by making use of the laws of quantum mechanics.

Most strikingly, quantum communication allows to transmit information with physical security guarantees at rates exceeding the capacities of classical links and quantum computers provide a means to speed up certain computations solving certain problems faster than any (present or future) classical computer.

One such problem is factoring large numbers into their primes.

This problem is the basis of much of modern cryptography such as the security of any information transfer through the internet. But the factoring problem was shown to be efficiently computable on a quantum computer using Shors algorithm. A functional quantum computer would therefore jeopardize the security of the internet.

Quantum computation with a discrete-variable system such as a two-level electron spin demands temperatures colder than those found in deep space.

However, continuous-variable systems, such as photons (particles of light) can operate at room temperatures and are more robust against decoherence, allowing for full miniaturization and mass manufacturing.

The theory of quantum error-correcting codes provides a new set of techniques to run a quantum algorithm with an arbitrary level of accuracy despite using imperfect noisy photons. Photonic quantum codes exhibit either translational or rotational symmetry in phase space. Potential of the latter has remained largely unexplored despite convincing evidence for a striking advantage.

In PhoQC, I will develop a novel stabilizer formalism to systematically study rotational symmetry in phase space.

I will find quantum codes operating on the entire or a part of the Hilbert space and I develop the corresponding universal logics.

We are at the dawn of the quantum computing age and the quantum codes and techniques developed in PhoQC will bring (photonic) quantum computation closer to industrial deployment.