Journal Club – 30/01/2024

Speaker: Hubert Lam

Venue and time: Thursday (30/01) — A003 — 11am

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https://cnrs.zoom.us/j/95302266086?pwd=VxUUSRuBlbMS5bLNzqKxDYXJLiq0Iv.1

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Upcoming journal clubs

Date	Speaker	Title	Article
16/01	Petr Steindl	Boosted fusion gates above the percolation threshold for scalable graph-state generation.	https://arxiv.org/abs/2412.18882
30/01	Hubert Lam	Scaling and networking a modular photonic quantum computer	https://www.nature.com/articles/s41586-024-08406-9
06/01	Samuel Hubert

Past journal clubs

Date	Speaker	Title	Abstract
30/01/2025	Hubert Lam	Scaling and networking a modular photonic quantum computer	https://www.nature.com/articles/s41586-024-08406-9
16/01/2025	Petr Steindl	Boosted fusion gates above the percolation threshold for scalable graph-state generation.	https://arxiv.org/abs/2412.18882
12/12/2024	Elianor Hoffmann	Distributed Quantum Computing in Silicon	https://arxiv.org/abs/2406.01704
05/12/2024	Noah Shofer	Fast optical control of a coherent hole spin in a microcavity.	https://arxiv.org/abs/2407.18876
28/11/2024	Etienne Bargel	Experimental photonic quantum memristor	https://www.nature.com/articles/s41566-022-00973-5
October 31,2024	Leonid Vidro	A short tutorial on Stabilizers and their connection to Graph States.	Leonid_slides_Jclub
October 7, 2024	Prashant Ramesh	Spin-photon entanglement of a single Er3+ ion in the telecom band	https://arxiv.org/abs/2406.06515
July 18, 2024	Lara Couronné	Generating tailored pulse sequences
July 4, 2024	George Crisan	A model for optimizing quantum key distribution with continuous-wave pumped entangled-photon sources	Quantum Key Distribution (QKD) allows unconditionally secure communication based on the laws of quantum mechanics rather then assumptions about computational hardness. Optimizing the operation parameters of a given QKD implementation is indispensable in order to achieve high secure key rates. So far, there exists no model that accurately describes entanglement-based QKD with continuous-wave pump lasers. For the first time, we analyze the underlying mechanisms for QKD with temporally uniform pair-creation probabilities and develop a simple but accurate model to calculate optimal trade-offs for maximal secure key rates. In particular, we find an optimization strategy of the source brightness for given losses and detection-time resolution. All experimental parameters utilized by the model can be inferred directly in standard QKD implementations, and no additional assessment of device performance is required. Comparison with experimental data shows the validity of our model. Our results yield a tool to determine optimal operation parameters for already existing QKD systems, to plan a full QKD implementation from scratch, and to determine fundamental key rate and distance limits of given connections.
June 13, 2024	Elham Mehdi	Two-Color Pump-Probe Measurement of Photonic Quantum Correlations Mediated by a Single Phonon	We propose and demonstrate a versatile technique to measure the lifetime of the one-phonon Fock state using two-color pump-probe Raman scattering and spectrally-resolved, time-correlated photon counting. Following pulsed laser excitation, the n = 1 phonon Fock state is probabilistically prepared by projective measurement of a single Stokes photon. The detection of an anti-Stokes photon generated by a second, time-delayed laser pulse probes the phonon population with sub-picosecond time resolution. We observe strongly non-classical Stokes-anti-Stokes correlations, whose decay maps the single phonon dynamics. Our scheme can be applied to any Raman-active vibrational mode. It can be modified to measure the lifetime of n >= 1 Fock states or the phonon quantum coherences through the preparation and detection of two-mode entangled vibrational states.
June 6, 2024	Prashant Ramesh	Qunnect: High rate distribution of polarization entangled photons from a bichromatic entanglement source across a metropolitan fiber network	Distributing high-fidelity, high-rate entanglement over telecommunication infrastructure is one of the main paths towards large-scale quantum networks, enabling applications such as quantum encryption and network protection, blind quantum computing, distributed quantum computing, and distributed quantum sensing. High-rate, robust entanglement sources that satisfy all the conditions necessary for implementing these technologies remains an outstanding experimental challenge. In this talk, we review two papers from the Qunnect team. In the first work, they present an entanglement source based on four-wave mixing in a diamond configuration in a warm rubidium vapor. They theoretically and experimentally investigate an alternative operating regime and demonstrate an entanglement source, which produces highly nondegenerate 795- and 1324-nm photon pairs. With this source they are able to achieve in-fiber pair-generation rates greater than 10^7/s, orders of magnitude higher than previously reported atomic entanglement sources. In the next work, they present a fully automated system capable of distributing polarization entangled photons over a 34 km deployed fiber in New York City. They achieve end-to-end pair rates of nearly 5 × 10^5 pairs/s and entanglement fidelity of approximately 99%. Separately, they achieve 15 days of continuous distribution, with a network up-time of 99.84%. Their work paves the way for practical deployment of 24/7 entanglement-based networks with rates and fidelity adequate for many current and future use-cases.
May 16, 2024	Valentin Guichard	Bird’s eye view of Quantum Matter 2024 – From Magnon scattering to implementation of Grover’s algorithm on a four-qubit silicon processor	The 4th edition of the Quantum Matter conference gathered various communities from quantum information and quantum matter together. In this journal club, I will give a general perspective on three different works from three different platforms. Starting from subwavelength imaging of magnonic excitation waves using scattering combined with a NV center-based magnetometer to probe both amplitude and phase of the scattered magnonic waves. It will follow with a roadmap presentation from IBM on both hardware and software to go from quantum utility toward quantum advantage, showing recent progress on hardware heavily limited by errors, requiring improvement in current error-correction codes. Finally, I will report on the implementation of Grover’s algorithm using a four-qubit quantum processor based on a Si:P quantum dot coupled to three nuclear spins. This study shows single qubit gates above 99.9% fidelities and CZ gates above 99% fidelity. They also demonstrate 3-qubit Greenberger-Horne-Zeilinger (GHZ) state with 96.2% fidelity.
May 2, 2024	Emilio Annoni	Partial indistinguishability theory for multi-photon experiments in multiport devices	Distinguishability is one of the relevant non idealities that limit the quality of quantum information processing with single photons. Through a powerful formalism, developed by V. Shchesnovich to describe photocounting experiments with linear optics, one is able to extend the concept of distinguishability beyond the two-photon scenario of the Hong-Ou-Mandel experiment. The physical insights given by this description will highlight the rich range of effects that distinguishability can produce in an n-photon experiment.[1] https://arxiv.org/abs/1410.1506 [2] http://arxiv.org/abs/1707.03893
April 25, 2024	Helio Huet	Fusion of deterministically generated photonic graph states	Entanglement has evolved from an enigmatic concept of quantum physics to a key ingredient of quantum technology. It explains correlations between measurement outcomes that contradict classical physics, and has been widely explored with small sets of individual qubits. Multi-partite entangled states build up in gate-based quantum-computing protocols, and – from a broader perspective – were proposed as the main resource for measurement-based quantum-information processing. The latter requires the ex-ante generation of a multi-qubit entangled state described by a graph. Small graph states such as Bell or linear cluster states have been produced with photons, but the proposed quantum computing and quantum networking applications require fusion of such states into larger and more powerful states in a programmable fashion. Here we achieve this goal by employing two individually addressable atoms in one optical resonator. Ring and tree graph states with up to eight qubits, with the names reflecting the entanglement topology, are efficiently fused from the photonic states emitted by the individual atoms. The fusion process itself employs a cavity-assisted gate between the two atoms. Our technique is in principle scalable to even larger numbers of qubits, and is the decisive step towards, for instance, a memory-less quantum repeater in a future quantum internet.

https://arxiv.org/abs/2403.11950

April 4, 2024Carlos MontenegroBrillouin spectroscopy in multilayered optophononic microcavities

Recently, there is a growing interest in engineering acoustic phonons inside microstructures for their potential applications in fields such as optoelectronics, quantum technologies and simulation of solid state systems. For the purpose of detecting high-frequency acoustic phonons, the inelastic scattering of light offers a means to measure these phonons in the frequency domain. However, standard Brillouin or Raman spectroscopy techniques face some challenges. For instance, optimizing the optics for the operating wavelengths, or filtering the scattered light from the excitation source in the spectra due to the sub-THz frequencies of the associated phonons. In this seminar, we discuss two recent techniques proposed in our team to enhance Brillouin spectroscopy measurement. Both methods use the opto-phononic microstructure to manipulate otherwise material intrinsic wave vector, cross-section, and polarization selection rules.[1] A. Rodriguez, P. Priya, O. Ortiz, P. Senellart, C. Gomez-Carbonell, A. Lemaître, M. Esmann, and N. D. Lanzillotti-Kimura, “Fiber-based angular filtering for high-resolution Brillouin spectroscopy in the 20-300 GHz frequency range,” Opt. Express 29, 2637-2646 (2021)[2] A. Rodriguez, P. Priya, E.R. Cardozo de Oliveira, A. Harouri, I. Sagnes, F. Pastier, L. Le Gratiet, M. Morassi, A. Lemaître, L. Lanco, M. Esmann, and N.D. Lanzillotti-Kimura, “Brillouin Scattering Selection Rules in Polarization-Sensitive Photonic Resonators”, ACS Photonics 10(6), 1687–1693 (2023).March 28, 2024Olivier Krebs A single-photon emitter coupled to a phononic-crystal resonator in the resolved-sideband regime

A promising route towards the heralded creation and annihilation of single-phonons is to couple a single-photon emitter to a mechanical resonator. The challenge lies in reaching the resolved-sideband regime with a large coupling rate and a high mechanical quality factor. We achieve all of this by coupling self-assembled InAs quantum dots to a small-mode-volume phononic-crystal resonator with mechanical frequency Ωm/2π=1.466 GHz and quality factor Qm=2.1×103. Thanks to the high coupling rate of gep/2π=2.9 MHz, and by exploiting a matching condition between the effective Rabi and mechanical frequencies, we are able to observe the interaction between the two systems. Our results represent a major step towards quantum control of the mechanical resonator via a single-photon emitter. https://arxiv.org/abs/2311.05342

April 4, 2024Carlos MontenegroBrillouin spectroscopy in multilayered optophononic microcavities

March 7, 2024

Adrià MedeirosAccessing the dynamics of a single spin with polarization-dependent projective measurements

Key challenges to harness charged semiconductor quantum dots (QD) as qubits are to measure and control the dynamic properties of the resident charge. Indeed, the spin coherence time is one of the limiting factors on the generation of cluster states. Current approaches rely on controlled sequences of pulses and repeated strong measurements of the spin state to measure either lifetime or coherence. Here, exploiting giant Kerr rotations, we introduce a time-dependent tomography protocol to probe the complete dynamics of a single spin in a micropillar cavity. This procedure is based on the interference between the reflected light from the cavity and the single photons from an electron confined in an InGaAs QD when applying a transverse magnetic field. The information of the electronic spin state is encoded on the polarization degree of freedom of the reflected light. By performing a polarization dependent measurement on a first photon, we access the conditional density matrix of the spin state. We track its evolution back to the stationary regime through the polarisation state measurement of the successive photons. With this time-dependent polarization tomography protocol, both the coherence (~2 ns) and the lifetime (~5 ns) of the electron spin can be inferred.

February 29, 2024Yann PortellaSingle-emitter quantum key distribution over 175 km of fibre with optimised finite key rates

Quantum key distribution with solid-state single-photon emitters is gaining traction due to their rapidly improving performance and compatibility with future quantum networks. Here we emulate a quantum key distribution scheme with quantum-dot-generated single photons frequency-converted to 1550 nm, achieving count rates of 1.6 MHz with g(2)(0) = 3.6 % and asymptotic positive key rates over 175 km of telecom fibre. We show that the commonly used finite-key analysis for non-decoy state QKD drastically overestimates secure key acquisition times due to overly loose bounds on statistical fluctuations. Using the tighter multiplicative Chernoff bound to constrain the estimated finite key parameters, we reduce the required number of received signals by a factor 108. The resulting finite key rate approaches the asymptotic limit at all achievable distances in acquisition times of one hour, and at 100 km we generate finite keys at 13 kbps for one minute of acquisition. This result is an important step towards long-distance single-emitter quantum networking.

February 22, 2024Petr Steindl

February 15, 2024

Sandeep SathyanTime-domain Brillouin scattering: Fundamentals & applications to depth-profiling and 3D imaging of materials

Time-domain Brillouin scattering (TDBS) is an experimental technique utilizing ultrafast lasers to generate and detect coherent acoustic pulses (CAPs) with nanometer-scale length and picosecond duration. Detection involves the interference of two probe light pulses: a weak one scattered by the CAP propagating in a transparent material, and a strong one reflected by various stationary interfaces of the sample. The transient optical reflectivity recorded by a photodetector as the CAP propagates contains information about the material’s local acoustic, optic, and acoustic-optic parameters. TDBS can be viewed as a potential extension of traditional frequency domain Brillouin microscopy, particularly useful when nanoscale depth resolution is required. Since its first demonstration for depth profiling nearly fifteen years ago [1,2], TDBS has found applications in imaging nanoporous films, ion-implanted semiconductors/dielectrics, plant and animal cells, texture in polycrystalline materials, temperature distributions in liquids, and monitoring the transformation of CAPs caused by absorption, diffraction, nonlinearity, and focusing [3]. In this talk, we delve into the fundamentals of TDBS and recent experimental advances made at the Laboratoire d’Acoustique de l’Université du Mans (LAUM), focusing primarily on TDBS applications for 3D imaging of individual grains of coexisting H2O ice phases at high pressure [4-7].1. C. Mechri, et al., Appl. Phys. Lett. 95, 091907 (2009).2. A. Steigerwald, et al., Appl. Phys. Lett. 94, 111910 (2009).3. V. E. Gusev and P. Ruello, Appl. Phys. Rev. 5, 031101 (2018).4. S. Sandeep, et al., J. Appl. Phys. 130, 053104 (2021).5. S. Sandeep, et al., Photoacoustics 33, 100547 (2023).

6. S. Sandeep, et al., Nanomaterials 11, 3131(2021).

7. S. Sandeep, et al., Nanomaterials 12, 1600 (2022).

February 9, 2024Ryuichi Ohta

Highly coherent photon-electron-phonon hybrid system using rare-earth ions

Rare-earth ions in crystals are attractive solid-state two-level systems owing to their very long coherence time at the excited and ground states. Their long-lived nature is preferable for various quantum applications, such as quantum memories and repeaters [1, 2], spin qubits [3], and quantum transducers [4], which play an essential role in quantum communication and computing. On-chip control of these stable states has been demonstrated by means of electric [5] and stress [6] fields, which enable the application of novel functionalities to quantum devices with rare-earth ions. Previous studies focused on the static field effects, which shift the resonance frequencies of the ions. However, rapid modulation of the fields enable the ions to be mixed with the driving fields leading to the coherent manipulation of the electrons [7], orbital state coupling [8], and laser cooling via two-level systems [9]. These field modulations have been reported with quantum dots and diamond color centers, but have not been observed with rare-earth ions. In this paper, we investigated the modulation of the energy levels of the excited states of erbium (Er) ions using surface acoustic wave (SAW) with a resonance frequency exceeding the optical linewidth of the ions. The modulated stress field generates multiple sideband peaks representing the optical excitation of the ions driven by the acoustic phonons. These spectra are well reproduced with our model based on the ensemble ions, which indicates that the optical excitation of the ions can be controlled by the acoustic drive. The results indicate the on-chip control of the transduction from the telecom photons for long-distance communications to long-lived solid-state excited electrons, which leads to the chip-integrated quantum memories and transducers.[1] D. L-Rivera et al, “Telecom-heralded entanglement between multimode solid-state quantum memories,” Nature 594, 37 (2021).[2] X. Liu et al, “Heralded entanglement distribution between two absorptive quantum memories,” Nature 594, 41 (2021).
[3] M. Raha et al, “Optical quantum nondemolition measurement of a single rare earth ion qubit,” Nat. Commun. 11, 1605 (2020).
[4] J. G. Bartholomew et al, “On-chip coherent microwave-to-optical transduction mediated by ytterbium in YVO4,” Nat. Commun. 11, 3266 (2020).[5] I. Craiciu et al, “Multifunctional on-chip storage at telecommunication wavelength for quantum networks,” Optica 8, 114 (2021).[6] R. Ohta et al, “Rare-earth-mediated opto-mechanical system in the reversed dissipation regime,” Phys. Rev. Lett. 126, 047404 (2021).
[7] D. A. Golter et al, “Coupling a surface Acoustic Wave to an Electron Spin in Diamond via a Dark State,” Phys. Rev. X 6, 041060 (2016).[8] H. Y. Chen et al, “Orbital State Manipulation of a Diamond Nitrogen-Vacancy Center Using a Mechanical Resonator,” Phys. Rev. Lett. 120,167401 (2018).

[9] M. Metcalfe et al., “Resolved Sideband Emission of InAs/GaAs Quantum Dots Strained by Surface Acoustic Waves,” Phys. Rev. Lett. 105,037401 (2010).

January 25, 2024Vincent VinelNonlinear Nanoresonators for Bell State Generation

Entangled photon states are a fundamental resource for optical quantum technologies and investigating the fundamental predictions of quantum mechanics. Up to now such states are mainly generated in macroscopic nonlinear optical systems with elaborately tailored optical properties. In this theoretical work, we extend the understanding on the generation of entangled photonic states toward the nanoscale regime by investigating the fundamental properties of photon-pair generation in sub-wavelength nonlinear nanoresonators. Taking materials with Zinc-Blende structure as an example, we reveal that such systems can naturally generate various polarization-entangled Bell states over a very broad range of wavelengths and emission directions, with little to no engineering needed. Interestingly, we uncover different regimes of operation, where polarization-entangled photons can be generated with dependence on or complete independence from the pumping wavelength and polarization, and the modal content of the nanoresonator. Our work also shows the potential of nonlinear nanoresonators as miniaturized sources of biphoton states with highly complex and tunable properties.

January 18, 2024Nico MargariaEverything you always wanted to know about single-photon sources fabrication*(*but were too afraid to ask)

In this science club I will go through all the steps needed to fabricate and fully characterize single-photon emitting device that many of us use. With emphasis on improvement feedbacks and the hidden tricky steps you may not be aware about. It is both to give everyone the basics on what is the device they are working with, but also refresh it for those who are already familiar.

January 11, 2024

Thibaut PolletCharge noise and spin noise in a semiconductor quantum device

Improving the quantum coherence of solid-state systems that mimic two-level atoms, for instance spin qubits or single-photon emitters using semiconductor quantum dots, involves dealing with the noise inherent to the device. Charge noise results in a fluctuating electric field, spin noise in a fluctuating magnetic field at the location of the qubit, and both can lead to dephasing and decoherence of optical and spin states. We investigate noise in an ultrapure semiconductor device using a minimally invasive, ultrasensitive local probe: resonance fluorescence from a single quantum dot. We distinguish between charge noise and spin noise through a crucial difference in their optical signatures. Noise spectra for both electric and magnetic fields are derived from 0.1 Hz to 100 kHz. The charge noise dominates at low frequencies, spin noise at high frequencies. The noise falls rapidly with increasing frequency, allowing us to demonstrate transform-limited quantum-dot optical linewidths by operating the device above 50 kHz.

November 23, 2023

Manuel GundínEnhanced Electron Spin Coherence in a GaAs Quantum Emitter

A spin-photon interface should operate with both coherent photons and a coherent spin to enable cluster-state generation and entanglement distribution. In high-quality devices, self-assembled GaAs quantum dots are near-perfect emitters of on-demand coherent photons. However, the spin rapidly decoheres via the magnetic noise arising from the host nuclei. In the paper I am presenting, the authors address this drawback by implementing an all-optical nuclear-spin cooling scheme on a GaAs quantum dot. The electron-spin coherence time increases 156-fold from T2∗ = 3.9 ns to 0.608 μs. The cooling scheme depends on a non-collinear term in the hyperfine interaction. The results show that such a term is present even though the strain is low and no external stress is applied. Their work highlights the potential of optically-active GaAs quantum dots as fast, highly coherent spin-photon interfaces.https://arxiv.org/abs/2307.02323

November 9, 2023

Andreas Fyrillas

Fifty shades of optimal control

In this science/journal club, we will discuss how machine learning can be harnessed to achieve optimal control of quantum devices. After examining how this applies to quantum dot single-photon sources, we will transpose the concepts to photonic integrated circuits. This introduction will serve as a basis for looking at the main points of the following article:Fyrillas, A., Faure, O., Maring, N., Senellart, J. & Belabas, N. Scalable machine learning-assisted clear-box characterization for optimally controlled photonic circuits. Preprint at https://doi.org/10.48550/arXiv.2310.15349 (2023).

October 26, 2023

Daniel Kimura

Playing in the time domain

Usually we are used to engineer acoustic and optical properties in the spatial domain, for example conceiving periodic structures to create photonic crystals. In this JC I will discuss two examples, one in acoustics and one in optics, where the change of properties takes place in the temporal domain, and discuss about the consequences and potential applications.