Microwave Quantum Photonics for Quantum Technology and Fundamental Physics

Introduction

With the proposed research programme, we plan to pioneer a platform that provides experimental access to the statistics of the microwave photons, thus opening up single-photon experiments in solid-state quantum devices.

Importance of Microwave Photons

Microwave photons play a major role throughout all solid-state quantum technology architectures, including:

• Superconducting qubits
• Charge qubits
• Spin qubits in semiconductors

They are used for control, coupling, and readout. However, the particle nature of the photons and, in particular, their statistical properties remain unexplored. The main roadblock here is the lack of suitable microwave photodetectors for performing continuous photon counting at high quantum conversion efficiency.

Development of Novel Sensors

We will create sensors probing the timing between two photons with time resolution better than the time–uncertainty Heisenberg limit of the individual photons.

Applications of New Measurement Tools

Thereby, we will create novel measurement tools applicable throughout the quantum technology field. In particular, the photon counting developed in this research programme will:

1. Open up the avenue to implement quantum computing based on so-called boson sampling with superconducting circuits.
2. Combine two key requirements for practical quantum computing:
   • The programmability of the superconducting circuits
   • The stronger quantum advantage of quantum processors based on boson sampling

Fundamental Insights

Beyond enabling these new measurement capabilities, we will generate unique experimental insights.

Correlated States and Many-Body Physics

The interplay between correlated bosonic and fermionic states — e.g., on how the bosonic particle statistics of the photons map onto the fermionic ones of the electrons — is likely to spur new experimental activities around many-body physics.

Understanding Quantum Measurements

Furthermore, the detection timing resolution beyond the Heisenberg limit will also shed light on the still unknown physics question of how measurements really work and act in the quantum physics domain.