Electrospray Ionization-Mass Spectrometry of Synthetic Polymers Functionalized with Carboxylic Acid End-Groups.

Electrospray ionization-mass spectrometry (ESI-MS) of low-charging synthetic polymers typically produces mass spectra exhibiting a bias toward the low-mass region of the polymer mass distribution. To examine the origin(s) of this ionization bias, narrow dispersity polystyrene polymers ( < 1.10) were prepared with ionizable carboxylic acid end-groups at one or both chain termini.

Local Versus Global Two-Photon Interference in Quantum Networks.

We devise an approach to characterizing the intricate interplay between classical and quantum interference of two-photon states in a network, which comprises multiple time-bin modes. By controlling the phases of delocalized single photons, we manipulate the global mode structure, resulting in distinct two-photon interference phenomena for time-bin resolved (local) and time-bucket (global) coincidence detection. This coherent control over the photons' mode structure allows for synthesizing two-photon interference patterns, where local measurements yield standard Hong-Ou-Mandel dips while the global two-photon visibility is governed by the overlap of the delocalized single-photon states.

A high dynamic range optical detector for measuring single photons and bright light.

Detecting light is fundamental to all optical experiments and applications. At the single photon level, the quantized nature of light requires specialised detectors, which typically saturate when more than one photon is incident. Here, we report on a massively-multiplexed single-photon detector, which exploits the saturation regime of a single click detector to exhibit a dynamic range of 123 dB, enabling measurement from optical energies as low as 10 photons per pulse to ∼ 2.

Supersymmetric Polarization Anomaly in Photonic Discrete-Time Quantum Walks.

Quantum anomalies lead to finite expectation values that defy the apparent symmetries of a system. These anomalies are at the heart of topological effects in electronic, photonic, and atomic systems, where they result in a unique response to external fields but generally escape a more direct observation. Here, we implement an optical-network realization of a discrete-time quantum walk, where such an anomaly can be observed directly in the unique circular polarization of a topological midgap state.

Probing measurement-induced effects in quantum walks via recurrence.

Measurements on a quantum particle unavoidably affect its state, since the otherwise unitary evolution of the system is interrupted by a nonunitary projection operation. To probe measurement-induced effects in the state dynamics using a quantum simulator, the challenge is to implement controlled measurements on a small subspace of the system and continue the evolution from the complementary subspace. A powerful platform for versatile quantum evolution is represented by photonic quantum walks because of their high control over all relevant parameters.