Project description

JRP Number: 20FUN05

JRP Title: Single- and entangled photon sources for quantum metrology (SEQUME)

JRP Timing:   Start:   01 June 2021 ,    End:    31 May 2024

Coordinating Organisation: PTB

JRP-Coordinator: Stefan Kück

Publishable summary – link

Planned work and objectives

The overall objective of the project is to develop bright entangled photon sources based on different application-oriented platforms and to exploit high-purity single-photon sources to demonstrate the quantum advantage achievable using these sources for specific measurements.

What will we do in SEQUME?

The specific objectives of the project are:

1. To assess single-photon sources and entangled-photon sources in traceable quantum-enhanced measurements (e.g. quantum calibration at the single-photon level, sub-shot noise measurements, quantum imaging, sub-diffraction imaging and quantum illumination), to overcome classical measurement limits (e.g. noise).

The project will go beyond the state of the art in objective 1 by designing, developing and implementing high performance single-photon and entangled photon sources for applications in enhanced quantum imaging. New paradigms of quantum measurements, such as weak values of quantum mechanical states and correlated measurements in HOM configurations will be explored as a tool for enhancing the resolution and sensitivity of microscopes and spectroscopic tools. Furthermore, the completely new aspect of traceability in quantum-enhanced measurements will be addressed.

2. To specify the performance parameters of single-photon and entangled-photon sources required to carry out different quantum-enhanced measurements.

In objective 2, the performance parameters for quantum-enhanced measurements based on Fock state sources will be explored, relying on single-photon sources as building blocks for non-classical light emission. Furthermore, performance parameters for quantum-enhanced measurements based on entangled-photon sources will be explored. Both investigations have not been carried out for metrological purposes so far and will be important with respect to further work in these fields.

3. To develop novel validated methods for the fabrication of single-photon sources and to optimise the sources for highest purity (g⁽²⁾(t = 0) close to 0), brightness (photon rate > 5 × 10⁶ photons per second) and indistinguishability (Hong-Ou-Mandel visibility > 95 %), according to the performance parameters specified in Objective 2.

The project will go beyond the state of the art in objective 3, by developing and optimising different methods for fabricating single-photon sources based on defects in diamond, on InGaAs/AlGaAs QDs and on single molecules, resulting in single-photon sources with highest purity (g⁽²⁾(t = 0) close to 0), brightness (photon rate > 5 × 10⁶ photons per second) and indistinguishability (Hong‑Ou‑Mandel visibility > 95 %).

4. To develop the European metrology infrastructure required for the traceable characterisation of entangled-photon and single-photon sources, i.e. detectors (including photon-number resolving detectors), amplifiers, as well as standardised quantum-optical setups for characterisation (in particular, entanglement tomography).

In objective 4, the project will go beyond the state of the art by developing the European metrology infrastructure required for the traceable characterisation of entangled-photon and single-photon sources even further, i.e. detectors (including photon-number resolving detectors), amplifiers as well as standardised quantum-optical setups for characterisation (in particular, entanglement tomography). Specifically for single-photon source (SPS) characterisation, a low photon flux calibration facility will be developed to measure photon flux down to a few fW, with transition-edge sensors showing high detection rate (~10 MHz), high quantum efficiency (> 90 %) and energy resolution better than 0.4 eV, novel photonic integrated circuit splitter 1:10⁶, and metrologically traceable high-accuracy calibration methods for SNSPD. This will demonstrate the applicability and assure uncertainty statements in low photon flux measurements using nonlinear femtosecond spectroscopy methods.

5. To facilitate the take up of the technology and measurement infrastructure developed in the project by the EMN Quantum, measurement supply chain, standards developing organisations (e.g. CEN and ISO) and end users (in the fields of quantum technology and nano-photonics).