Sabine Wollmann

University of Bristol | UB · Centre for Quantum Photonics

We demonstrate the generation of unbalanced two-photon entanglement in the Laguerre–Gaussian (LG) transverse-spatial degree-of-freedom, where one photon carries a fundamental (Gauss) mode and the other a higher-order LG mode with a non-zero azimuthal (ℓ) or radial (p) component. Taking a cue from the N00N state nomenclature, we call these types of...

We demonstrate the generation of unbalanced two-photon entanglement in the Laguerre-Gaussian (LG) transverse-spatial degree-of-freedom, where one photon carries a fundamental (Gauss) mode and the other a higher-order LG mode with a non-zero azimuthal ($\ell$) or radial ($p$) component. Taking a cue from the $N00N$ state nomenclature, we call these...

As a measure of the 'closeness' of two quantum states, fidelity plays a fundamental role in quantum information theory. Fidelity estimation protocols try to strike a balance between information gleaned from an experiment, and the efficiency of its implementation, in terms of the number of states consumed by the protocol. Here we adapt a previously...

Verifying entanglement between parties is essential for creating a secure quantum network, and Bell tests are the most rigorous method for doing so. However, if there is any signaling between the parties, then the violation of these inequalities can no longer be used to draw conclusions about the presence of entanglement. This is because signaling...

Frequency comb absorption spectroscopy combined with low-noise, fast homodyne measurements provide a toolbox for ultra-sensitive absorption measurements. Integrating these schemes on photonic platforms to bring them closer to practical applications is challenging. Here, we propose a scheme that can be readily adapted on a photonic platform. We show...

Quantum fluctuations in the intensity of an optical probe is noise which limits measurement precision in absorption spectroscopy. Increased probe power can offer greater precision; however, this strategy is often constrained by sample saturation. Here, we analyze measurement precision for a generalized absorption model in which we account for satur...

Quantum fluctuations in the intensity of an optical probe is noise which limits measurement precision in absorption spectroscopy. Increased probe power can offer greater precision, however, this strategy is often constrained by sample saturation. Here, we analyse measurement precision for a generalised absorption model in which we account for satur...

We analyze and experimentally demonstrate quantum steering using criteria based on generalized entropies and criteria with minimal assumptions based on the so-called dimension-bounded steering. Further, we investigate and compare their robustness against experimental imperfections such as misalignment in the shared measurement reference frame. Whil...

We demonstrate quantum steering based on generalised entropies and criteria with minimal assumptions based on the so-called dimension-bounded steering. Further, we investigate their robustness against experimental imperfections such as misalignment in the shared measurement reference-frame.

We analyse and experimentally demonstrate quantum steering using criteria based on generalised entropies and criteria with minimal assumptions based on so-called dimension-bounded steering. Further, we investigate and compare their robustness against experimental imperfections such as misalignment in the shared measurement reference frame. Whilst e...

Einstein-Podolsky-Rosen steering is a quantum phenomenon wherein one party influences, or steers, the state of a distant party’s particle beyond what could be achieved with a separable state, by making measurements on one-half of an entangled state. This type of quantum nonlocality stands out through its asymmetric setting and even allows for cases...

Einstein-Podolsky-Rosen steering is a quantum phenomenon wherein one party influences, or steers, the state of a distant party's particle beyond what could be achieved with a separable state, by making measurements on one half of an entangled state. This type of quantum nonlocality stands out through its asymmetric setting, and even allows for case...

We prove and experimentally demonstrate that EPR-steering can be rigorously asymmetric, unlike Bell tests, by constructing quantum states which are steerable in one direction, whilst two-way steering is impossible with arbitrary quantum measurements.

We theoretically and experimentally investigate a strong uncertainty relation valid for any $n$ unitary operators, which implies the standard uncertainty relation as a special case, and which can be written in terms of geometric phases. It is saturated by every pure state of any $n$-dimensional quantum system, generates a tight overlap uncertainty...

Einstein-Podolsky-Rosen steering refers to the quantum phenomenon whereby the state of a system held by one party can be "steered" into different states at the will of another, distant, party by performing different local measurements. Although steering has been demonstrated in a number of experiments involving qubits, the question of which two-qub...

Entanglement is the key resource for many long-range quantum information tasks, including secure communication, networking quantum computers, and remote processing of quantum information. As the characteristic trait of quantum mechanics, it is also important for testing quantum physics over long distances or in different reference frames. Robust ve...

Protocols for testing or exploiting quantum correlations-such as entanglement, Bell nonlocality, and Einstein-Podolsky-Rosen steering- generally assume a common reference frame between two parties. Establishing such a frame is resource-intensive, and can be technically demanding for distant parties. While Bell nonlocality can be demonstrated with h...

Das erstmals 1935 von Albert Einstein, Boris Podolsky und Nathan Rosen beschriebene Phänomen der Verschränkung liegt fundamentalen Quantenkommunikationsprotokollen wie der Teleportation zu Grunde. Hierin sind zwei oder mehr Quantenpartner über eine “spukhafte Fernwirkung”, wie Einstein sagte, miteinander verbunden. Diese Art der Verschränkung ist s...

Within the hierarchy of inseparable quantum correlations, Einstein-Podolsky-Rosen steering is distinguished from both entanglement and Bell nonlocality by its asymmetry—there exist conditions where the steering phenomenon changes from being observable to not observable, simply by exchanging the role of the two measuring parties. While this one-way...

We present a source of polarization entangled photon pairs based on spontaneous parametric downconversion engineered for frequency uncorrelated telecom photon generation. Our source provides photon pairs that display, simultaneously, the key properties for high-performance quantum information and fundamental quantum science tasks. Specifically, the...

We demonstrate a single step quantum relay, allowing quantum steering for verifying entanglement between distant parties with detection loophole closed even in the presence of very high channel loss.

Within the hierarchy of inseparable quantum correlations, Einstein-Podolsky-Rosen steering is distinguished from both entanglement and Bell nonlocality by its asymmetry -- there exist conditions where the steering phenomenon changes from being observable to not observable, simply by exchanging the role of the two measuring parties. Whilst this one-...

Colloidal particles are a versatile physical system which have found uses across a range of applications such as the simulation of crystal kinetics, etch masks for fabrication, and the formation of photonic band-gap structures. Utilization of colloidal particles often requires a means to produce highly ordered, periodic structures. One approach is...