Light sources for applications in quantum information, quantum-enhanced sensing and quantum metrology are attracting increasing scientific interest. To gain inside into the underlying physical processes of quantum light generation, efficient photon detectors and experimental techniques are required to access the photon statistics. In this work, we employ photon-number-resolving (PNR) detectors based on superconducting transition-edge sensors (TESs) for the metrology of photonic microstructures with semiconductor quantum dots (QDs) as emitters. For the PNR analysis, we developed a state of the art PNR detection system based on fiber-coupled superconducting TESs. Our stand-alone system comprises six tungsten TESs, read out by six 2-stage-SQUID current sensors, and operated in a compact detector unit integrated into an adiabatic demagnetization refrigerator. This PNR detection system enables us to directly access the photon statistics of the light field emitted by our photonic microstructures. In this contribution, we focus on the PNR study of deterministically fabricated quantum light sources emitting single indistinguishable photons as well as twin-photon states. Additionally, we present a PNR-analysis of electrically pumped QD micropillar lasers exhibiting a peculiar bimodal behavior. Employing TESs our work provides direct insight into the complex emission characteristics of QD- based light sources. We anticipate, that TES-based PNR detectors, will be a viable tool for implementations of photonic quantum information processing relying on multi-photon states.
John Bell’s theorem of 1964 states that local elements of physical reality, existing independent of measurement, are inconsistent with the predictions of quantum mechanics (Bell, J. S. (1964), Physics (College. Park. Md). Specifically, correlations between measurement results from distant entangled systems would be smaller than predicted by quantum physics. This is expressed in Bell’s inequalities. Employing modifications of Bell’s inequalities, many experiments have been performed that convincingly support the quantum predictions. Yet, all experiments rely on assumptions, which provide loopholes for a local realist explanation of the measurement. Here we report an experiment with polarization-entangled photons that simultaneously closes the most significant of these loopholes. We use a highly efficient source of entangled photons, distributed these over a distance of 58.5 meters, and implemented rapid random setting generation and high-efficiency detection to observe a violation of a Bell inequality with high statistical significance. The merely statistical probability of our results to occur under local realism is less than 3.74×10<sup>-31</sup>, corresponding to an 11.5 standard deviation effect.
SRON is developing an electronic system for the multiplexed read-out of an array of transition edge sensors (TES) by
combining the techniques of frequency domain multiplexing (FDM) with base-band feedback (BBFB). The astronomical
applications are the read-out of soft X-ray microcalorimeters and the far-infrared bolometers for the SAFARI instrument
on the Japanese mission SPICA. In this paper we derive the requirements for the read-out system regarding noise and
dynamic range in the context of the SAFARI instrument, and demonstrate that the current experimental prototype is
capable of simultaneously locking 57 channels and complies with these requirements.
X-ray microcalorimeters using magnetic sensors show great promise for use in astronomical x-ray spectroscopy.
We have begun to develop technology for fabricating arrays of magnetic calorimeters for X-ray astronomy. The
magnetization change in each pixel of the paramagnetic sensor material due to the heat input of an absorbed
x-ray is sensed by a meander shaped coil. With this geometry it is possible to obtain excellent energy sensitivity,
low magnetic cross-talk and large format arrays fabricated on wafers that are separate from the SQUID read-out.
We report on the results from our prototype arrays, which are coupled to low noise 2-stage SQUIDs developed
at the PTB Berlin. The first testing results are presented and the sensitivity compared with calculations.
The EURECA (EURopean-JapanEse Calorimeter Array) project aims to demonstrate the science performance and
technological readiness of an imaging X-ray spectrometer based on a micro-calorimeter array for application in future
X-ray astronomy missions, like Constellation-X and XEUS. The prototype instrument consists of a 5 × 5 pixel array of
TES-based micro-calorimeters read out by by two SQUID-amplifier channels using frequency-domain-multiplexing
(FDM). The SQUID-amplifiers are linearized by digital base-band feedback. The detector array is cooled in a cryogenfree
cryostat consisting of a pulse tube cooler and a two stage ADR. A European-Japanese consortium designs,
fabricates, and tests this prototype instrument. This paper describes the instrument concept, and shows the design and
status of the various sub-units, like the TES detector array, LC-filters, SQUID-amplifiers, AC-bias sources, digital
Initial tests of the system at the PTB beam line of the BESSY synchrotron showed stable performance and an X-ray
energy resolution of 1.58 eV at 250 eV and 2.5 eV @ 5.9 keV for the read-out of one TES-pixel only. Next step is
deployment of FDM to read-out the full array. Full performance demonstration is expected mid 2009.
EURECA (EURopean-JapanEse Calorimeter Array) comprises a 5 x 5 pixel imaging TES-based micro-calorimeter
array read-out by SQUID-based frequency-domain-multiplexed electronics and cooled down by an adiabatic
demagnetization refrigerator. A European-Japanese consortium designs, fabricates, and tests this prototype instrument
with the aim to show within about 2 years technology readiness of a TES-based X-ray imaging micro-calorimeter array
in anticipation of future X-ray astronomy missions, like XEUS (ESA), Constellation-X (NASA), NEXT (JAXA), DIOS
(JAXA), ESTREMO (ASI), and NEW (Dutch-multinational). This paper describes the instrument concept, and shows
the design of the various sub-units, like the TES detector array, LC-filters, SQUID-amplifiers, flux-locked-loop
electronics, AC-bias sources, etc.