Polarisation Entangled Photon Emitter

Lead Research Organisation: University of Glasgow
Department Name: College of Science and Engineering


Quantum technologies will transform and improve crucial aspects of our life. To name a few, they will protect our privacy, and secure digital communications from any cyber attack, push the speed of computers to new levels, enable imaging the faintest objects, with applications to security and healthcare.
While few of these outcomes are moving towards commercialisation, such as quantum-secured communications, others are still far from being a robust technology.
The UK government has invested substantial resources in promoting the translation of the science available in academic institutions into technologies for the benefit of the public.
For this quantum revolution to happen, we need to combine the know-how available in the academia, the technical capabilities of our high-tech companies, and the feedback from potential users of the technology.
With this proposal, we are following this receipt, targeting the development of the first commercial source of visible, entangled photons, suitable for applications ranging from secure communication to metrology.

Entangled light is the key to unlock the possibilities offered by quantum mechanics, and is the starting point for many applications, such quantum-key distribution and quantum computing. The components required to build an entangled light source are a laser and a suitable crystal that converts the laser light into entangled photons.

Chromacity is a UK leader in the market of laser systems while Covesion is a world leader in the supply of crystals for the generation of entangled photons. We propose therefore to partner with these companies bringing our know-how in quantum optics. The University of Glasgow is indeed a leading institution in the UK, and the world, for what concern quantum optics and quantum technologies. Together, we have the production capabilities, the engineering skills, and the supply chain, to bring a visible source of entangled photons on the market.

The role of the academic team in this project is twofold. On the one hand, we shall guide the design of the optical components required to generate the entangled states, starting from the technology provided by the two partner companies. We shall exploit our experience in the generation of entangled states in a lab to inform the two companies on the best choice of the nonlinear crystals parameters, the geometry of the laser interaction with the nonlinear elements, and on the proper measurement procedure required to quantify the level of entanglement achieved. This will be, therefore, a knowledge transfer action, aimed at bringing the academic know-how into a commercial reality. On the other hand, we will test the results produced by the joint work of Chromacity and Covesion. In this scenario, the University of Glasgow team will be the beta-tester. We are indeed end-users in the potential quantum-optical market since most of our research requires entangled states to be carried on. We shall, therefore, provide our feedback to the companies, concerning performances, packaging and user-friendliness. As the research in quantum optics becomes increasingly common in academia, a growing number of researchers will look for "plug and play" sources of entangled states.

Planned Impact

This project aims at developing a compact source of visible entangled photon pairs, and infrared correlated photon pairs.
This activity is expected to:
- Contribute to the development of secure communications at visible wavelengths. This includes, for instance, applications to free-space, satellite, and underwater quantum key distribution.
- Contribute to the development of infrared communications. This mostly addresses quantum key distribution via infrared optical fibres, at a longer wavelength concerning the current, 1550nm standard.
- Contribute to the development of quantum-enhanced metrology and imaging. This includes high-sensitivity phase measurements for academic research on the medium term, and quantum-enhanced imaging for, e.g. biological applications, on a longer run.

By combining two UK technology providers, Chromacity and Covesion, with the academic partners and end-users, we intend helping to lay the basis for the UK quantum technology, by setting up a strategic supply chain for the commercialisation of quantum states of light.


10 25 50
Description The first result is the characterisation of a photon pair source at 2um. Port of the result is the development of know-how on the components and issues that arise when operating in this mainly unexplored spectral region.
The second key result is the observation of quantum interference at 694nm that underpins the generation of visible polarisation entangled photon pairs. Also, in this case, one of the most critical aspects is the development of the know-how associated with this specific wavelength.
Exploitation Route Our results will be instrumental to the development of the 2um photonic platform, especially concerning secure communication (quantum key distribution). With the progress of the award, we realised that there was a diffused demand for investigations into the 2um spectral region especially for what concerns the communication between ground and satellites. Indeed, the 2um region is less affected by the solar background concerning the shorter wavelengths currently used. We attended a European Space Agency workshop were this point become evident and we, therefore, focused on the further development of the 2um technology.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Education,Security and Diplomacy

Description With this project, we have developed a source of visible polarisation entangled photons and 2um wavelength photon pairs driven by the laser of our commercial partner Chromacity and employing specifically designed nonlinear crystal developed by our industrial partner Covesion. These findings are now used to investigate the potential impact of communication with polarisation entangled 2um radiation. Besides, our findings contributed to the development of new products by our industrial partners.
First Year Of Impact 2019
Sector Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Education,Security and Diplomacy
Impact Types Cultural,Societal,Economic

Title Second Harmonic Generation in AlGaAs-On-Insulator Waveguides 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Title Terahertz control of air lasing 
Description The dataset includes all the raw data that are analysed and presented in the related publication. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Title Ultra-broadband terahertz coherent detection via silicon nitride-based deep sub-wavelength metallic slit 
Description We present a novel class of CMOS-compatible devices aimed to operate the solid-state-biased coherent detection of ultrashort terahertz pulses, i.e. featuring gap-free bandwidth at least two decades-wide. Such a structure relies on 1-?m-wide slit aperture between two parallel aluminum pads and embedded in a 1-?m-thick layer of silicon nitride, deposited on a quartz substrate. We show that such a device can detect ultra-broadband terahertz pulses by employing unprecedented low optical probe energies of only a few tens of nanojoule, due to the more than one order of magnitude higher nonlinear coefficient of silicon nitride with respect to silica, which was employed in the previous generations. In addition, very high static electric fields can be generated within the slit by applying extremely low external bias voltages (in the order of few tens of volts), which strongly enhance the dynamic range of the detected THz waveforms. Finally, we show how this new device potentially enables to operate the solidstate- biased technique with a homodyne scheme, in a similar manner to electro-optic sampling. These results pave the way to the integration of the solid-state ultra-broadband detection in compact and miniaturized terahertz systems fed by high repetitionrate laser oscillators and low-noise, low-voltage generators. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes