Quantum technologies promise a variety of completely new applications. In addition to quantum computers, quantum sensing and quantum communication are among the areas of quantum technology in which the first, also commercially successful product developments are expected. The Federal Ministry of Education and Research is now funding Humboldt University Berlin (HU) in two new collaborative projects in the field of quantum technologies.

Researchers are working on the novel QEED microscopy for quantum-based early cancer diagnostics. Image: LaVision BioTec GmbH

The first funded project, QEED, deals with quantum sensing with entangled photons - for applications in medical research and cancer diagnostics. Funded as a BMBF "Lighthouse Project" for 5 years (project volume 11.9 million euros, HUB 1.7 million euros), the collaboration will jointly develop a very powerful microscope that can work in the mid-infrared (MIR). In order to transfer measurement information from the clinically relevant MIR to the near infrared (NIR), which can be detected particularly fast and with low noise, a novel, spectrally resolving imaging method based on entangled photon pairs will be used.

In the "Nonlinear Quantum Optics" group at HU and IRIS Adlershof, led by Dr. Sven Ramelow, who also serves as scientific director of the overall collaboration, high-performance quantum interferometer modules are being developed and the quantum sensing measurement techniques underlying the collaborative project are being optimized. The core innovation here is the significant increase in the rate of generated entangled photon pairs, as well as the significant extension of the MIR measurement range compared to the state-of-the-art.

Among the total of ten project partners are five research institutions - including three from Berlin: FBH-Berlin, Charité-Berlin, and HU-Berlin. Also five corporate partners are part of the team and will, in addition to their work in the project, after project completion promote a commercialization of the microscope and its components. The project officially started on 01.01.23.

The second funded collaborative project named "High Performance Light Sources for Quantum Communication" - MIHQU (project volume 5.3 million Euro, HUB 1.4 million Euro) is about quantum communication - an important building block for the future security of digital infrastructures in our society. In quantum communication, the exchange of cryptographic keys is based on the laws of physics, which means that security, in contrast to currently used encryption, remains fundamentally guaranteed - even in the event of attacks by novel, previously unknown algorithms or by powerful quantum computers.

Image: AIXEMTEC GmbH, Herzogenrath

The goal of the project is to miniaturize sources for photon pairs in such a way that their reproducible industrial production can be established in small series. At Humboldt-Universität, the group "Nonlinear Quantum Optics" is mainly working on the development of functional models of the sources as a basis for the subsequent integration.

In addition to the HU-Berlin (Dr. Sven Ramelow with his group "Nonlinear Quantum Optics"), the total of 5 project partners includes the Deutsches Zentrum für Luft- und Raumfahrt e.V., Berlin in the person of Prof. Janik Wolters, who will coordinate the project, as well as the Technische Universität Berlin, and two company partners – son-x GmbH, Aachen and AIXEMTEC GmbH, Herzogenrath. The project started on 01.03.2023.

Infobox: Nonlinear interferometers with entangled photons
Spontaneous parametric down-conversion (SPDC) in nonlinear optical crystals is a standard process for generating correlated or entangled photon pairs for quantum communication, quantum-assisted imaging or quantum sensing. If one now uses two identical SPDC processes that are coherently pumped and superimposes the emissions, one can observe simultaneous, identical interference for both photons of a pair - the so-called signal and idler photons. Such a setup as shown in the figure below represents such a so-called "nonlinear interferometer". (Chekhova, Ou, “Nonlinear interferometers in quantum optics“, AOP 8, 1, 104 (2016)).

Schematic of a nonlinear interferometer, here in Mach-Zehnder configuration


The essential point is that the entangled photon pairs interfere as a single quantum object! This means that a phase (or absorption) of the idler photons also affects the signal photons as an interference signal (and vice versa). The interference pattern - i.e. its phase position and contrast - thus depends on the transmission coefficients of pump radiation, idler and signal photons as well as on the total phase difference (ϕ_s+ ϕ_i - ϕ_p) that all three waves have accumulated in the interferometer. In particular, the phase and absorptions of the idler can thus be determined solely by measuring the signal photons. This effect is called "measurement with non-detected photons", since the actual "measuring" Idler photons never have to be measured themselves. If photon pairs are now generated with a large wavelength spread (e.g. signal in the visible, idler in the mid-infrared), the spectral information (absorption, dispersion) recorded by the idler photons in the MIR can be registered by measuring the wavelength-dependent interference in the signal with a silicon detector. These are particularly powerful and low-noise and thus enable a variety of very practical applications of this measurement principle.

Dr. Edgar Nandayapa introduces the HyD group and explains solar cell printing.

We would like to thank Pablo and Laura, who organized the whole thing again!

V.l.n.r.: Dirk Radzinski (CEO, xolo), Prof. Stefan Hecht (CSO, xolo), Frank Cartsen Herzog (HZG Group), Dr. Elisabeth Schrey (DeepTech & Climate Fonds), Tobias Faupel (DeepTech & Climate Fonds), Dr. Anna Christmann (Bundesministerium Wirtschaft und Klimaschutz)

The Berlin-based company xolo was founded in Berlin in 2019 by IRIS Adlershof- member Stefan Hecht, Martin Regehly and Dirk Radzinski. With Xolography, they have developed a novel volumetric 3D printing technology that prints quickly and produces very smooth surfaces. Xolography uses two beams of light with different wavelengths that collide in the resin and harden it into the desired material. This enables a resolution of a few micrometers. The process is many times faster than previous methods and enables centimetre-sized objects to be printed in a few seconds instead of several hours as was previously the case. This makes printing cheaper and potentially more rewarding for mass production. It also does not rely on formative support structures and allows the use of materials previously unsuitable for 3D printing.

xolo Aneurisma Print Source: xolo, youtube

Xolo has now received eight million euros from Deep Tech & Climate Fonds (DTCF), HZG Group, Onsight Ventures and Square One to enable the transition to industrial scale use. The first 10 devices were delivered specifically to research institutes to test different fields of application, e.g. in medical technology for the reproduction of organs or in optics for the production of high-precision lenses.
The investment is intended to help xolography achieve a breakthrough and strengthen Germany as a location for industry and research.

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