About EPJ

The European Physical Journal (EPJ) is a series of peer-reviewed journals covering the whole spectrum of physics and related interdisciplinary subjects. EPJ is committed to high scientific quality in publishing and is indexed in all main citation databases.

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EPJ QT Highlight - How does Earth’s spacetime deformation affect quantum communications?

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Credit: CQT, National University of Singapore

Jan Kohlrus investigates relativitic effects to consider when setting up quantum communication systems.

The interplay and overlap between relativity and quantum theory are among the most complex and challenging open problems of modern theoretical physics. This grey area has been extensively studied on the theoretical side, sometimes following very speculative and exotic directions, while very few experiments have been proposed in a way that rigorously incorporates relativity and quantum features.

The purpose of our work is to propose feasible experiments that involve quantum fields in a relativistic framework. In our recent article in EPJ Quantum Technology, we study how observers that undergo different motion, and experience different strengths of the gravitational field, measure pulses of light that propagate from one user to another. In particular, we look at quantum communication schemes between Earth and satellite links, as well as between two satellites.

Continue reading Jan’s post here.

EPJ QT Highlight - Quantum security from small satellites

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Credit: CQT, National University of Singapore

Shoebox sized satellites could be the key to fast-track development of space quantum communication, writes author Daniel Oi in a contribution to the SpringerOpen blog.

Quantum computing threatens the security of public key cryptosystems that secure the internet. But what quantum takes away, it can also give back. The technique of quantum key distribution (QKD) promises codes that are guaranteed by physics to be, in principle, unbreakable.

In EPJ Quantum Technology, we propose a CubeSat Quantum Communications Mission (CQuCoM) with a vision towards a globe-spanning constellation of QKD satellites. We are an international consortium of six research entities and one company across six countries.

Continue reading the blog post here.

EPJ Quantum Technology Review - Macroscopic Quantum Resonators (MAQRO): 2015 update

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Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schrödinger’s cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to limited free-fall times and the quality of vacuum and microgravity. The proposed mission Macroscopic Quantum Resonators (MAQRO) may overcome these limitations and allow researchers to address such fundamental questions. MAQRO harnesses recent developments in quantum optomechanics, high-mass matter-wave interferometry as well as state-of-the-art space technology to push macroscopic quantum experiments towards their ultimate performance limits and to open new horizons for applying quantum technology in space. The main scientific goal is to probe the vastly unexplored ‘quantum-classical’ transition for increasingly massive objects, testing the predictions of quantum theory for objects in a size and mass regime unachievable in ground-based experiments. The hardware will largely be based on available space technology.

In this review article, the authors present the MAQRO proposal submitted in response to the ESA's 4th Cosmic Vision call for a medium-sized mission (M4) with a possible launch in 2025, and review the progress with respect to the original MAQRO proposal made in 2010. In particular, the updated proposal overcomes several critical issues of the original proposal by relying on established experimental techniques from high-mass matter-wave interferometry and by introducing novel ideas for particle loading and manipulation. Moreover, the mission design was improved to better fulfil the stringent environmental requirements for macroscopic quantum experiments.

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