Max Planck Institute of Quantum Optics

Interferometers are known for precise measurements of the effects inside of them. Here we show that placing a Dove prism in one of the interferometer arms allows for also detecting minute effects happening outside the device. We derive how the additional reflection in one arm can amplify small tilts or displacements of the input beam in the dark output port of the interferometer, in analogy to weak value amplification. The experiment demonstrates a clear improvement of the measurement signal. Moreover, in the bright output port, small disturbances in the input beam get largely filtered, thereby enabling beam stabilization with a fully passive device.

We characterize the dynamical state of many-body bosonic and fermionic many-body models with intersite Gaussian couplings, on-site non-Gaussian interactions, and local dissipation comprising incoherent particle loss, particle gain, and dephasing. We first establish that, for fermionic systems, if the dephasing noise is larger than the non-Gaussian interactions, irrespective of the Gaussian coupling strength, the system state is a convex combination of Gaussian states at all times. Furthermore, for bosonic systems, we show that if the particle loss and particle gain rates are larger than the Gaussian intersite couplings, the system remains in a separable state at all times. Building on this characterization, we establish that at noise rates above a threshold, there exists a classical algorithm that can efficiently sample from the system state of both the fermionic and bosonic models. Finally, we show that, unlike fermionic systems, bosonic systems can evolve into states that are not convex Gaussian even when the dissipation is much higher than the on-site non-Gaussianity. Similarly, unlike bosonic systems, fermionic systems can generate entanglement even with noise rates much larger than the intersite couplings.

We investigate the properties of an impurity immersed in an ensemble of spin-polarized fermions confined in a tight quantum wire. We use a non-perturbative variational approach that accounts for virtual transverse excitations and regularizes the zero-range interaction. We compute the polaron's energy, effective mass, and spectral weight, and benchmark our results against the exactly solvable Yang-Gaudin model of a purely 1D system. While the two models agree in the weakly interacting regime, we find significant deviations in the strongly attractive limit, including a divergence of the effective mass and evidence for a polaron-to-molecule transition inherited from the underlying 3D physics, which is absent in the purely 1D description. Our work quantifies the accuracy of quasi-1D systems as analog quantum simulators and highlights the emergence of beyond-1D physics even in nominally 1D settings.

We present a numerical method to simulate a system of multiple emitters coupled to a noninteracting bath in any parameter regime. Our method relies on a Block Lanczos transformation that maps the whole system onto a strip geometry whose width is given by the number of emitters. Utilizing the spatial symmetries of the problem and identifying the relevant range of energies of the bath, we achieve a more efficient simulation, which we perform using tensor network techniques. As a demonstration, we study the collective emission from multiple emitters coupled to a square lattice of bosons and observe how the departure from Markovianity as coupling strength and emitter number is increased prevents collective radiation. We also simulate the dynamic preparation of an excitation in a bound state from a multiexcitation initial state. Our work opens possibilities for the systematic exploration of non-Markovian effects in the dynamics and equilibrium properties of multiemitter systems. Furthermore, it can easily be extended to other setups, including finite bath temperature or impurities coupled to fermionic environments.

Abstract The control of light’s various degrees of freedom underpins modern physics and technology, from quantum optics to telecommunications. Ultraintense lasers represent the pinnacle of this control, concentrating light to extreme intensities at which electrons oscillate at relativistic velocities within a single optical cycle. These extraordinary conditions offer unique opportunities to probe the fundamental aspects of light–matter interactions and develop transformative applications. However, the precise characterization of intense, ultrashort lasers has lagged behind our ability to generate them, creating a bottleneck in advancing laser science and its applications. Here we present the first single-shot vector field measurement technique for intense, ultrashort laser pulses that provides an unprecedented insight into their complete spatiotemporal and polarization structure, including quantified uncertainties. Our method efficiently encodes the full vector field onto a two-dimensional detector by leveraging the inherent properties of these laser pulses, allowing for real-time characterization. We demonstrate its capabilities on systems ranging from high-repetition-rate oscillators to petawatt-class lasers, revealing subtle spatiotemporal couplings and polarization effects. This advancement bridges the gap between theory and experiment in laser physics, providing crucial data for simulations and accelerating the development of novel applications in high-field physics, laser–matter interactions, future energy solutions and beyond.

Born at the dawn of the new millennium, attosecond “photography” has opened the door for capturing subatomic motions as they evolve in time. Control of the oscillating electric field of light has permitted the attosecond control of electrons with unprecedented precision in space and time.

Field-resolved infrared spectroscopy (FRS) based on electro-optic sampling (EOS) measures directly in time domain the electric response field emitted by molecules, vibrationally excited by few-cycle mid-infrared (MIR) laser pulses [1]. The response field provides a fingerprint of the molecular composition of the sample, with potential applications in biomedical diagnostics [2]. For sufficiently long decoherence times, the sample signal can be separated from the excitation-pulse via time filtering, enabling background-free detection [1] - however, at the expense of losing the information at early times. Many biologically relevant molecules like proteins have significant overlap of the molecular signal with the excitation window. In order to reveal the full response signal and reduce the influence of the excitation noise at early times, we introduced differential molecular fingerprinting (dMF) [3], [4]. The approach uses broadband interferometry to optically suppress the infrared excitation-pulse after interaction with the sample. Here, we demonstrate, for the first time, the application of octave-spanning mid-infrared dMF for the measurement of liquid samples.

Toward multi-octave spanning molecular spectroscopy, Cr:ZnS femtosecond oscillators are regarded among the most promising mid-infrared sources [1]. By employing nonlinear compression using a TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plate [2], these oscillators provide carrier-envelope-phase stable single-cycle pulses at 2.2 μm and support highly efficient spectral down-conversion to the 3–12 μm spectral range [3]. Further bandwidth extension, ultimately reaching the sub-terahertz regime, is expected to enhance the reliability of molecular identification through vibrational spectroscopy. However, there are few reports on far-infrared to terahertz generation based on 2-micron femtosecond oscillators [4]. In this study, we present, for the first time, broadband terahertz generation and detection based on optical rectification from a Cr:ZnS femtosecond oscillator.

Echo-based spectroscopy of the superhyperfine interaction of an electronic spin with nuclear spins in its surroundings enables detailed insights into the microscopic magnetic environment of spins in solids. Still, it is an outstanding challenge to resolve individual nuclear spins in a dense bath, in which many of them exhibit a comparable coupling strength. This simultaneously requires a high spectral resolution and a large signal-to-noise ratio. However, when probing spin ensembles, dipolar interactions between the dopants can lead to a concentration-dependent trade-off between resolution and signal. Here, we fully eliminate this limitation of previous optical-echo-envelope-modulation spectroscopy experiments by integrating the emitters into a high-finesse resonator, which allows for strong optical echoes even at very low concentrations. To demonstrate its potential, the technique is applied to erbium dopants in yttrium orthosilicate (Er:YSO). Achieving an unprecedented spectral resolution enables precise measurements of the superhyperfine interaction with four of the Y nuclear spins densely surrounding each emitter. The achieved boost of the signal, enabled by the resonator, allows for extending the approach to the lowest concentration possible—to the level of single dopants, thereby providing a tool for detecting and studying individual nuclear spins. Thus, our technique paves the way for an improved understanding of dense nuclear-spin baths in solids.

We propose a novel mid-infrared dual electro-optic comb spectroscopy method with high spectral resolution based on spectral interleaving. It offers a frequency resolution of 100 MHz, providing a bandwidth of 486 GHz.