Prof. Dr. Christine Silberhorn and her team (University of Paderborn) recently demonstrated the first device that combines frequency conversion with high efficiency and bandwidth compression of single photons. The device, which is based on non-linear waveguides in Lithium Niobate manufactured in the group in Paderborn, allows to adapt photons from sources in the telecom range to atomic systems in the visible and near-infrared spectrum, paving the…
Direct probing scheme. Two-mode squeezed states are generated with the process of parametric down-conversion. One of the two modes is overlapped with a reference beam at a beam splitter. Both modes are then measured with photon-number detectors. From their statistics, the amplitude correlations and hence the squeezing can be inferred.
The characterization of quantum states is an essential part of quantum optics. One particular task is the estimation of squeezing in so called two-mode squeezed states.
In a recent publication in Physical Review Letters*, researchers from the integrated quantum optics group in Paderborn in collaboration with theoretical physicists from Olomouc in the Czech Republic and Madrid in Spain have demonstrated a method to measure such squeezing in a…
Response curves of the TES detector. Each of the 500 shown traces is a raw detection event. The traces already indicate the discretization of energy levels, i.e. the photon number of each input pulse. With further post processing of these traces, photon numbers up to 20 can be detected with single-photon resolution and up to 100 with a few-photon resolution.
The generation of macroscopic quantum states is a challenging goal throughout many fields of physics. Not only would it be fascinating to see quantum effects on a macroscopic scale, their generation is also a prerequisite if one wants to exploit quantum effects for real-world applications.
In a joint publication, recently published in Physical Review Letters*, scientists from two groups at the University of Paderborn, the IQO and the MQO, in…
Implementation Scheme: (a) One pattern of a dynamically
changing graph with 3 sites used in the experiment (shown explicitly for
3 steps). The full set of patterns used in the experiment is denoted by
K'n for n steps. The input state (blue arrow) is evolved (red arrow) and
measured tomographically at every step. (b) Implementation scheme of the
example, the R and T operators are represented by filled and hollow
diamonds, respectively. (c) Setup scheme of the time-multiplexed PQW.
According to the implementation scheme the walker always alternates
between paths A and B. The colour coding is used to mark corresponding
entities in both panels. We average over all patterns to obtain the open
system’s dynamics.
[Scientific Reports 5, 13495 (2015)]
The aim for understanding transport phenomena is at the heart of many studies on processes in nature and man-made structures ranging from photosynthesis to information network applications. Recent research indicates that the combination of classical with quantum effects can explain or introduce highly unexpected behaviour of the overall system. In order to understand quantum transport processes on a random or…
Rebeccah Grotemeyer defended her bachelor's thesis with the title "Comparison of classically excited modes and modes excited through parametric down-conversion".
The working principle of a time multiplexing detector: A single pulse of photons is split and recombined with various time delays producing a train of pulses with less than one photon per pulse. These pulses are send onto avalanche photo diodes producing 'click' or 'no-click' events. Counting the number of clicks gives information about the number of photons present in the initial pulse, but the exact relation between photon number distributions and measured click-statistics is complex because the click statistics are influenced by the number of beam splitters, the detector response functions and the losses in the system.
Scientists in the group of Christine Silberhorn in Paderborn and the group of Werner Vogel in Rostock have demonstrated a new method to identify nonclassical correlations between two parties sharing a quantum state. The method allows to characterize quantum states and resources in a simple and straight forward way. The results are published in Uncovering Quantum Correlations with Time-Multiplexed Click Detection, Phys. Rev. Lett. 115, 023601…
