Tjerk Oosterkamp is awarded an NWO Large Grant of 2.5 million euro to build a machine that offers an environment with ultra-high vacuum and very low temperatures, only one thousandth of a degree above absolute zero. This will provide many More info
research groups with the opportunity to conduct groundbreaking research under unprecedented conditions. The facility will be unique in the world and its future place in the low-vibration lab at the new Leiden science campus gives it even larger capabilities.
On the level of the quantum world at room temperature, particles swarm and vibrate wildly. Physicists learn about this miniature world by very precisely studying a small sample plate containing ‘entangled’ particles. Surely they are unhappy with the chaotic situation at room temperature that quickly destroys the very fragile entwined state that they want their particles to be in. Just imagine gluing a broken pot back together in a hurricane. And without a proper vacuum, the sample plate will get contaminated immediately by unwanted atoms on the sample surface. So add a dust storm to the hurricane scenario.
Quantum physicists need extremely low temperatures and an ultra-high vacuum to perform their research. Only then, their sample will stay clean and its particles stay entangled. Oosterkamp’s new machine will offer exactly that. In just over a year, physicists can come to Leiden to:
- Investigate unexplored quantum effects at ultra-low temperatures
- Explore new measurement methods to detect phenomena of intertwined electrons in materials that are said to ‘quantum compute all by themselves’
- Explore the infamous quantum measurement problem in the context of systems containing highly entangles particles
The 2.5 million euro vacuum fridge offers its state-of-the-art environment to a variety of instruments: scanning gates, scanning tunneling microscopes, atomic force microscopes and magnetic resonance force microscopes.
A schematic drawing of the system, featuring a dilution refrigerator which offers space for up to four scanning probe microscopes at the coldest plate at the bottom (10 mK with nuclear demag possibilities to Publ. 11-02-2016 17:49
An ambitious plan to add a new angle to the hunt for dark matter has passed an important landmark. A collaboration of particle physicists and theorists, with a leading role for Leiden University’s Alexey Boyarsky, has proposed an experiment to More info
try and create ‘sterile’ neutrinos with the so-called Super Proton Synchrotron (SPS). This instrument is part of the particle lab CERN in Geneva. The SPS council has now endorsed the experiment, meaning that the proposal will go into a three year process of testing. If the CERN council finally approves, the 185 million euro Search for Hidden Particles (SHiP) Experiment will kick-off in 2026.
Boyarsky is on a quest to unravel the nature of one of the most mysterious phenomena in the Universe. The cosmos appears to consist for the larger part out of mass we cannot see. We have no idea where it comes from. Physicists call this ‘dark matter’. Sterile neutrinos are candidate building blocks of dark matter. However, it has never been proven that these hypothetical particles even exist at all.
If they do exist, they would have an extremely weak or even no interaction with ordinary matter. The proposed SHiP experiment uses SPS’s high-intensity proton beam to try and produce heavy sterile neutrinos, which should occasionally decay into normal matter. The collaboration expects the protons to create the sought-after particles through a chain of events, after which they would be able to indirectly prove their existence by measuring signature decay signals.
Boyarsky reached an important landmark in his attempt to set up a 185 million euro experiment that uses this Super Proton Synchrotron at CERN to prove the existence of sterile neutrinos.
Michel Orrit is honoured with the Physica prize 2016 for his groundbreaking work on single molecule spectroscopy. In the mid ‘80s, Orrit came to the realization that it should be possible to optically detect a single molecule. A few years More info
later, in 1990, he indeed became the first one to detect the fluorescence signal of one molecule.
Last year, the Nobel Prize in Chemistry was awarded to Betzig, Hell and Moerner for the development of super-resolved fluorescence microscopy. The Nobel Committee’s description of the scientific background clearly showed the groundbreaking significance of Orrit’s experiment as the basis for the super-resolution techniques that were established afterwards. Moerner measured a single molecule slightly before Orrit, using absorption, but Orrit’s measurement using fluorescence produced much less background noise and became the standard in this scientific field.
Orrit’s work gave rise to a whole new research area; single molecule/particle optics. Since he started working at the Leiden Institute of Physics, he has built up a very active research group. Recently they developed a ‘nano microphone’—a microphone consisting of only one molecule.
For the first time, scientists have entangled four photons in their orbital angular momentum. Leiden physicists sent a laser through a crystal, thereby creating four photons with coupled ‘rotation’. So far this has only been done for two photons. The More info
discovery makes uncrackable secret communication of complex information possible between multiple parties. Publication in Physical Review Letters on February 1st. Pre-print on Arxiv
Entanglement holds a great promise, with applications in perfectly secret communication and quantum computing. If two photons are created simultaneously, they are each other’s counterpart, so that their ‘rotation’ is always reversed with respect to the other. If we measure left ‘rotation’ for one photon, then the other will always ‘rotate’ to the right after measurement with a similar filter. This is called entanglement. Before the measurement, each photon’s ‘rotation’ is undetermined.
This ‘rotation’ is a property of photons that scientists discovered in 1992 in Leiden; physicists call this orbital angular momentum. And this property has more than two values. It covers an infinitely large alphabet of information. So with this you can transfer much more information per photon than with a property like polarization, which contains only two possible values. In 2001, scientists managed to entangle two photons in orbital angular momentum for the first time. Now, Leiden physicist Wolfgang Löffler and his colleagues are the first ones to entangle four photons in this way. They announce it in an Editor’s suggestion article in Physical Review Letters. The discovery offers many extra possibilities, like sending an uncrackable encrypted message to more than one party.
During their successful experiment, the researchers sent short ultraviolet laser pulses of two picoseconds through a crystal. Occasionally this leads to the creation of four entangled photons. This is extremely rare, but by generating 80 million pulses per second they managed to detect on average two so-called photon quadruplets each second. To confirm these were indeed entangled in orbital angular momentum, the team used a spatial phase modulator that converts this ‘rotation’ back to light travelling as a plane wave. They registered this ‘normal’ light with single photon detectors.
Observation of four-photon orbital angular momentum entanglement, B. C. Hiesmayr, M, J. A. de Dood, W. Löffler, Physical Review Letters. Pre-print on Arxiv.
Leiden physicists sent short ultraviolet laserpulses of two picoseconds through a crystal. This leads to the creation of four photons that are entangled in their orbital angular momentum—here depicted as red blue spirals. The rainbow colored circles illustrate the phase (color) and intensity (brightness) of the photon’s cross section.
Tulotta C, Stefanescu C, Beletkaia E, Bussmann J, Tarbashevich K, Schmidt T, Snaar-Jagalska BE (2016) Inhibition of cross-species CXCR4 signaling by the small molecule IT1t impairs triple negative breast cancer early metastases in zebrafish., Dis Model Mech. [Abstract][DOI][pdf]
T.G.A. Verhagen, H.N. Tinkey, H.C. Overweg, M. van Son, M. Huber,J.M. van Ruitenbeek and J. Aarts (2016) Temperature dependence of spin pumping
and Gilbert damping in thin Co/Pt bilayers, J. Phys.: Condensed Matter, 28, 056004. [DOI]
18 Feb, 16:00, GL - Cell Observatory
van Leeuwenhoek lecture on BioScience Tecumseh Fitch , Vienna: The biology and evolution of language: A comparative approach Read more
2 March, 19:30, Sitterzaal 032
Colloquim Ehrenfestii Dam Son (Chicago): Emergent relativistic fermions on the half-filled Landau level
8 March, 15:00, Academy building
Thesis Defense Vicente Atal - Instituut-Lorentz: "On multifield inflation, adiabaticity, and the speed of sound of the curvature perturbations" Promotor: Prof.dr. A. Achúcarro, co-promotor: Prof.dr. G.A. Palma (Univ. de Chile, Santiago)