BZPEERReading, trust and collaboration for research
Menu

Discover

GraphFollow connections around a paper, topic or saved view.

Workspaces

HomePick up where your research flow left off.InboxHandle requests, replies and notifications from one place.CollectionsCurate reading lists, evidence sets and shareable dossiers.ResearchSee your private provenance graph, trail and imports.CollaborationMove from discovery into focused discussion rooms.PublishDraft, preview and publish full-text research articles.

Network

ExpertsFind specialists worth following or asking for help.CommunitiesJoin research circles organized around shared work.PartnersSee external organizations active around the same topics.

Opportunities

ListingsBrowse roles, calls and collaborations with clearer fit signals.

Account

Log inReturn to your reading and collaboration workspace.Create accountStart saving work, following people and joining teams.
Log inCreate account

Researcher profile

Christoph Simon

Christoph Simon contributes to research discovery and scholarly infrastructure.

ResearcherAffiliation not importedOpen to collaborate
quant-phBiological PhysicsNeurons and Cognitionphysics.chem-phcond-mat.mtrl-scicond-mat.quant-gasnlin.PSphysics.atom-phphysics.soc-ph

Trust snapshot

Quick read

Trust 21 - EmergingVerification L1Unclaimed author
13works
0followers
9topics
4close collaborators

Actions

Decide how to stay connected

Follow researcher0

Identity and collaboration

How to connect with this researcher

Claiming links this public author record to a researcher profile and unlocks direct collaboration workflows.

Log in to claim

Direct collaboration

Open a focused conversation when the fit is right

Claim this author entity first to unlock direct invitations.

Research graph

See the researcher in context

Open full explorer

Inspect adjacent work, topics, institutions and collaborators without jumping out to a separate graph page.

Building this graph slice

BZPEER is loading the nearby papers, people, topics and institutions for this page.

Published work

13 published item(s)

preprint2026arXiv

Modeling Optical Polarization Evolution in Myelinated Axon Waveguides with Realistic Imperfections

Biophotonic signaling via axons has been proposed as a potential mode of neural communication, where information might be encoded not only in photon number and wavelength but also in polarization. Although earlier computational studies have examined how structural imperfections influence optical transmission, their effects on polarization fidelity remain unexplored; previous modeling of polarization fidelity in myelinated axons has largely focused on idealized geometries. This study incorporates three structural imperfections characteristic of axons in vivo: variation in myelin thickness, non-circular cross-sectional geometry, and axonal bending, within a model that includes four nodes of Ranvier. We find that variation in myelin thickness alone has minimal impact on fidelity, while non-circular cross-sections show strong mode dependence. Axonal bending has the most significant influence, generating large fluctuations and deep fidelity dips. When all imperfections are combined in a single axon model, the simulations show substantial drops in fidelity, yet certain modes exhibit recovery, with repeated revivals reaching values of around 0.8, which exceeds the revivals observed in the single imperfection cases. Overall, the results indicate that although structural imperfections affect polarization, polarization-based biophotonic signals might remain recoverable even in realistic axons, lending support to the plausibility of polarization-based biophotonic signaling in the brain.

0 citations0 reviewsNo code linkedOpen access
preprint2023arXiv

Hypomagnetic field effects as a potential avenue for testing the radical pair mechanism in biology

Near-zero magnetic fields, called hypomagnetic fields, are known to impact biological phenomena, including developmental processes, the circadian system, neuronal and brain activities, DNA methylation, calcium balance in cells, and many more. However, the exact mechanism underlying such effects is still elusive, as the corresponding energies are far smaller than thermal energies. It is known that chemical reactions involving radical pairs can be magnetic field dependent at very low intensities comparable to or less than the geomagnetic field. Here, we review in detail hypomagnetic field effects from the perspective of the radical pair mechanism, pointing out that under certain conditions, they can be comparable or even stronger than the effects of increasing the magnetic field. We suggest that hypomagnetic field effects are an interesting avenue for testing the radical pair mechanism in biology.

0 citations0 reviewsNo code linkedOpen access
preprint2022arXiv

Chimera patterns in conservative systems and ultracold atoms with mediated nonlocal hopping

Experimental realizations of chimera patterns, characterized by coexisting regions of phase coherence and incoherence, have so far only been achieved for non-conservative systems with dissipation. Moreover, theoretical studies of chimera patterns have also been limited either to the non-conservative case or to simplified models that describe the dynamics only in terms of a scalar phase field. Here, we show for the first time explicitly that the formation of chimera patterns can also be observed in conservative Hamiltonian systems with nonlocal hopping in which both energy and particle number are conserved, and where the local phase and amplitude are non-separable even in the weak coupling regime. Effective nonlocality can be realized in a physical system with only local coupling if different time scales exist, which we illustrate by a minimal conservative model with an additional mediating channel. Finally, we show that chimera patterns should be observable in ultracold atomic systems: Nonlocal spatial hopping over up to tens of lattice sites with independently tunable hopping strength and on-site nonlinearity can be implemented in a two-component Bose-Einstein condensate with a spin-dependent optical lattice, where the untrapped component serves as the matter-wave mediating field.

0 citations0 reviewsNo code linkedOpen access
preprint2022arXiv

Magnetic field effects in biology from the perspective of the radical pair mechanism

A large and growing body of research shows that weak magnetic fields can significantly influence various biological systems, including plants, animals, and humans. However, the underlying mechanisms behind these phenomena remain elusive. It is remarkable that the magnetic energies implicated in these effects are much smaller than thermal energies. Here we review these observations, of which there are now hundreds, and we suggest that a viable explanation is provided by the radical pair mechanism, which involves the quantum dynamics of the electron and nuclear spins of naturally occurring transient radical molecules. While the radical pair mechanism has been studied in detail in the context of avian magnetoreception, the studies reviewed here show that magnetosensitivity is widespread throughout biology. We review magnetic field effects on various physiological functions, organizing them based on the type of the applied magnetic fields, namely static, hypomagnetic, and oscillating magnetic fields, as well as isotope effects. We then review the radical pair mechanism as a potential unifying model for the described magnetic field effects, and we discuss plausible candidate molecules that might constitute the radical pairs. We review recent studies proposing that the quantum nature of the radical pairs provides promising explanations for xenon anesthesia, lithium effects on hyperactivity, magnetic field and lithium effects on the circadian clock, and hypomagnetic field effects on neurogenesis and microtubule assembly. We conclude by discussing future lines of investigation in this exciting new area of quantum biology related to weak magnetic field effects.

0 citations0 reviewsNo code linkedOpen access
preprint2022arXiv

Photons guided by axons may enable backpropagation-based learning in the brain

Despite great advances in explaining synaptic plasticity and neuron function, a complete understanding of the brain's learning algorithms is still missing. Artificial neural networks provide a powerful learning paradigm through the backpropagation algorithm which modifies synaptic weights by using feedback connections. Backpropagation requires extensive communication of information back through the layers of a network. This has been argued to be biologically implausible and it is not clear whether backpropagation can be realized in the brain. Here we suggest that biophotons guided by axons provide a potential channel for backward transmission of information in the brain. Biophotons have been experimentally shown to be produced in the brain, yet their purpose is not understood. We propose that biophotons can propagate from each post-synaptic neuron to its pre-synaptic one to carry the required information backward. To reflect the stochastic character of biophoton emissions, our model includes the stochastic backward transmission of teaching signals. We demonstrate that a three-layered network of neurons can learn the MNIST handwritten digit classification task using our proposed backpropagation-like algorithm with stochastic photonic feedback. We model realistic restrictions and show that our system still learns the task for low rates of biophoton emission, information-limited (one bit per photon) backward transmission, and in the presence of noise photons. Our results suggest a new functionality for biophotons and provide an alternate mechanism for backward transmission in the brain.

0 citations0 reviewsNo code linkedOpen access
preprint2022arXiv

Proposal for room-temperature quantum repeaters with nitrogen-vacancy centers and optomechanics

We propose a quantum repeater architecture that can operate under ambient conditions. Our proposal builds on recent progress towards non-cryogenic spin-photon interfaces based on nitrogen-vacancy centers, which have excellent spin coherence times even at room temperature, and optomechanics, which allows to avoid phonon-related decoherence and also allows the emitted photons to be in the telecom band. We apply the photon number decomposition method to quantify the fidelity and the efficiency of entanglement established between two remote electron spins. We describe how the entanglement can be stored in nuclear spins and extended to long distances via quasi-deterministic entanglement swapping operations involving the electron and nuclear spins. We furthermore propose schemes to achieve high-fidelity readout of the spin states at room temperature using the spin-optomechanics interface. Our work shows that long-distance quantum networks made of solid-state components that operate at room temperature are within reach of current technological capabilities.

0 citations0 reviewsNo code linkedOpen access
preprint2022arXiv

Proposal for transduction between microwave and optical photons using $\mathrm{^{167}Er}$-doped yttrium orthosilicate

Efficient transduction devices that reversibly convert optical and microwave quantum signals into each other are essential for integrating different technologies. Rare-earth ions in solids, and in particular Erbium ions, with both optical and microwave addressable transitions are promising candidates for designing transducers. We propose a microwave-to-optical quantum transducer scheme based on the dark state protocol in $\mathrm{^{167}Er}$ doped into yttrium orthosilicate (YSO) at zero external magnetic fields. Zero-field operation is beneficial for superconducting resonators that can incur extra losses in magnetic fields. By calculating the fidelity and efficiency of the transducer, considering the most important imperfections, we show that an efficient conversion is possible with a high fidelity. We also investigate the microwave transitions of $\mathrm{^{167}Er}$:YSO that can be used for the transducer protocol.

0 citations0 reviewsNo code linkedOpen access
preprint2022arXiv

The emerging commercial landscape of quantum computing

Quantum computing technologies are advancing, and the class of addressable problems is expanding. Together with the emergence of new ventures and government-sponsored partnerships, these trends will help lower the barrier for new technology adoption and provide stability in an uncertain market. Until then, quantum computing presents an exciting testbed for different strategies in an emerging market.

0 citations0 reviewsNo code linkedOpen access
preprint2021arXiv

$\textit{Ab initio}$ and group theoretical study of properties of the $\text{C}_\text{2}\text{C}_\text{N}$ carbon trimer defect in h-BN

Hexagonal boron nitride (h-BN) is a promising platform for quantum information processing due to its potential to host optically active defects with attractive optical and spin properties. Recent studies suggest that carbon trimers might be the defect responsible for single-photon emission in the visible spectral range in h-BN. In this theoretical study, we combine group theory together with density functional theory (DFT) calculations to predict the properties of the neutral $\text{C}_\text{2}\text{C}_\text{N}$ carbon trimer defect. We find the multi-electron states of this defect along with possible radiative and non-radiative transitions assisted by the spin-orbit and the spin-spin interactions. We also investigate the Hamiltonian for external magnetic field and ground-state hyperfine interactions. Lastly, we use the results of our investigation in a Lindblad master equation model to predict an optically detected magnetic resonance (ODMR) signal and the $g^2(τ)$ correlation function. Our findings can have important outcomes in quantum information applications such as quantum repeaters used in quantum networks and quantum sensing.

0 citations0 reviewsNo code linkedOpen access
preprint2020arXiv

Analyzing photon-count heralded entanglement generation between solid-state spin qubits by decomposing the master equation dynamics

We analyze and compare three different schemes that can be used to generate entanglement between spin qubits in optically-active single solid-state quantum systems. Each scheme is based on first generating entanglement between the spin degree of freedom and either the photon number, the time bin, or the polarization degree of freedom of photons emitted by the systems. We compute the time evolution of the entanglement generation process by decomposing the dynamics of a Markovian master equation into a set of propagation superoperators conditioned on the cumulative detector photon count. We then use the conditional density operator solutions to compute the efficiency and fidelity of the final spin-spin entangled state while accounting for spin decoherence, optical pure dephasing, spectral diffusion, photon loss, phase errors, detector dark counts, and detector photon number resolution limitations. We find that the limit to fidelity for each scheme is restricted by the mean wavepacket overlap of photons from each source, but that these bounds are different for each scheme. We also compare the performance of each scheme as a function of the distance between spin qubits.

0 citations0 reviewsNo code linkedOpen access
preprint2020arXiv

Cavity-assisted controlled phase-flip gates

Cavity-mediated two-qubit gates, for example between solid-state spins, are attractive for quantum network applications. We propose three schemes to implement a controlled phase-flip gate mediated by a cavity. The main advantage of all these schemes is the possibility to perform them using a cavity with high cooperativity, but not in the strong coupling regime. We calculate the fidelity of each scheme in detail, taking into account the most important realistic imperfections, and compare them to highlight the optimal conditions for each scheme. Using these results, we discuss which quantum system characteristics might favor one scheme over another.

0 citations0 reviewsNo code linkedOpen access
preprint2020arXiv

Teleportation Systems Towards a Quantum Internet

Quantum teleportation is essential for many quantum information technologies including long-distance quantum networks. Using fiber-coupled devices, including state-of-the-art low-noise superconducting nanowire single photon detectors and off-the-shelf optics, we achieve quantum teleportation of time-bin qubits at the telecommunication wavelength of 1536.5 nm. We measure teleportation fidelities of >=90% that are consistent with an analytical model of our system, which includes realistic imperfections. To demonstrate the compatibility of our setup with deployed quantum networks, we teleport qubits over 22 km of single-mode fiber while transmitting qubits over an additional 22 km of fiber. Our systems, which are compatible with emerging solid-state quantum devices, provide a realistic foundation for a high-fidelity quantum internet with practical devices.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Near-term performance of quantum repeaters with imperfect ensemble-based quantum memories

We study the feasibility of meaningful proof-of-principle demonstrations of several quantum repeater protocols with photon (single-photon and photon-pair) sources and atomic-ensemble based quantum memories. We take into account non-unit memory efficiencies that decay exponentially with time, which complicates the calculation of repeater rates. We discuss implementations based on quantum dots, parametric down-conversion, rare-earth-ion doped crystals, and Rydberg atoms. Our results provide guidance for the near-term implementation of long-distance quantum repeater demonstrations, suggesting that such demonstrations are within reach of current technology.

0 citations0 reviewsNo code linkedOpen access