arXiv subjects

Christoph Baune

Publications and source records attributed to Christoph Baune.

6 recordsLinked to original sources

arXiv2022

Compact Michelson interferometers with subpicometer sensitivity

The network of interferometric gravitational-wave observatories has successfully detected tens of astrophysical signals since 2015. In this paper, we experimentally investigate compact sensors that have the potential to improve the sensitivity of gravitational-wave detectors to intermediate-mass black holes. We use only commercial components, such as sensing heads and lasers, to assemble the setup and demonstrate its subpicometer precision. The setup consists of a pair of Michelson interferferometers that use deep frequency modulation techniques to obtain a linear, relative displacement readout over multiple interference fringes. We implement a laser-frequency stabilisation scheme to achieve a sensitivity of 0.3\,$\text{pm} / \sqrt{\text{Hz}}$ above 0.1\,Hz. The device has also the potential to improve other experiments, such as torsion balances and commercial seismometers.

physics.ins-det↗

arXiv2017

Negative Wigner function at telecommunication wavelength from homodyne detection

Quantum states of light having a Wigner function with negative values represent a key resource in quantum communication and quantum information processing. Here, we present the generation of such a state at the telecommunication wavelength of 1550nm. The state is generated by means of photon subtraction from a weakly squeezed vacuum state and is heralded by the `click' of a single photon counter. Balanced homodyne detection is applied to reconstruct the Wigner function, also yielding the state's photon number distribution. The heralding photons are frequency up-converted to 532nm to allow for the use of a room-temperature (silicon) avalanche photo diode. The Wigner function reads W(0,0)=-0.063 +/- 0.004 at the origin of phase space, which certifies negativity with more than 15 standard deviations.

quant-ph↗

arXiv2016

Unconditional entanglement interface for quantum networks

Entanglement drives nearly all proposed quantum information technologies. By up-converting part of a 1550 nm two-mode squeezed vacuum state to 532 nm, we demonstrate the generation of strong continuous-variable entanglement between widely separated frequencies. Nonclassical correlations were observed in joint quadrature measurements of the 1550 and 532 nm fields, showing a maximum noise suppression 5.5 dB below vacuum. Our versatile technique combines strong nonclassical correlations, large bandwidth, and in principle, the ability to entangle the telecommunication wavelength of 1550 nm with any optical wavelength.

quant-ph↗

arXiv2016

Quantum non-Gaussianity of frequency up-converted single photons

Nonclassical states of light are an important resource in today's quantum communication and metrology protocols. Quantum up-conversion of nonclassical states is a promising approach to overcome frequency differences between disparate subsystems within a quantum information network. Here, we present the generation of heralded narrowband single photons at 1550 nm via cavity enhanced spontaneous parametric downconversion (SPDC) and their subsequent up-conversion to 532 nm. Quantum non-Gaussianity (QNG), which is an important feature for applications in quantum information science, was experimentally certified for the first time in frequency up-converted states.

quant-ph↗

arXiv2016

Strongly squeezed states at 532 nm based on frequency up-conversion

Quantum metrology utilizes nonclassical states to improve the precision of measurement devices. In this context, strongly squeezed vacuum states of light have proven to be a useful resource. They are typically produced by spontaneous parametric down-conversion, but have not been generated at shorter wavelengths so far, as suitable nonlinear materials do not exist. Here, we report on the generation of strongly squeezed vacuum states at 532 nm with 5.5 dB noise suppression by means of frequency up-conversion from the telecommunication wavelength of 1550 nm. The up-converted states are employed in a model Mach-Zehnder interferometer to illustrate their use in quantum metrology.

quant-ph↗

arXiv2013

Weak-signal conversion from 1550nm to 532nm with 84% efficiency

We report on the experimental frequency conversion of a dim, coherent continuous-wave light field from 1550nm to 532nm with an external photon-number conversion efficiency of (84.4 +/- 1.5)%. We used sum-frequency generation, which was realized in a standing-wave cavity built around a periodically poled type I potassium titanyl phosphate (PPKTP) crystal, pumped by an intense field at 810 nm. Our result is in full agreement with a numerical model. For optimized cavity coupler reflectivities it predicts a conversion efficiency of up to 93% using the same PPKTP crystal.

quant-ph↗