Toward entangled photon pair generation @ nanoscale
One of the major challenges faced in the development of quantum computers and quantum communication is the integration of devices for generating single photons and photon pairs. In this context, a drastic reduction of the size of devices entails a significant drop in their efficiency of photon generation. One way to overcome this challenging obstacle is to excite local electric field by coupling the emitter to plasmonic nano-antennas.
Recently we have achieved this objective by coupling an emitter which is a non-linear nanocrystal to nano-antennas by placing it within the gap of two antennas. Hence, creating a hybrid nano-structure in order to generate an enhancement by a factor that is 1000 times higher than an isolated nanocrystal. Therefore, the objective of the project is to use experimental as well as theoretical or numerical tools to further optimize second order non-linear processes such as second harmonic generation (SHG) and spontaneous parametric down conversion (SPDC) to enhance their efficiency to several orders of magnitude higher than what is already demonstrated. If successful, this would enable the first ever detection of photon pairs with the so called hybrid plasmonic nanostructure using the experimental setup that we have built.
The groundwork towards achieving this goal has already been completed with the pioneering work conducted during the course of three thesis defended in 2018 and 2019. With the development of a quantitative and numerical tool, the optimal configuration to obtain a strong coupling between the non-linear crystal and plasmonic antenna can be determined. This step therefore involves adapting the developed numerical programmes to new plasmonic antenna configurations, in particular, bowtie and to also search for the best materials (Al, Au, Ag) to obtain plasmonic resonances as well as for nonlinear nanocrystals (in particular for nano-iodates developed by Géraldine Dantelle and organic crystals synthesized by Alain Ibanez at the Néel Institute or for other compounds developed by already established collaborations). In the next step, the hybrid structures will be fabricated at the NanoFab platform of the institute using a technique that was recently realized which allows to place the nano-antennas with precision around the desired non-linear crystal as per its efficiency. In the final step, the hybrid nano-structures will be characterized for SHG emission (using an experimental setup and a technique that has already been realized with extremely reliable results) as well as for SPDC if sufficient enhancement is obtained which will allow us to demonstrate for the first time the generation and detection of photon pairs in hybrid plasmonic nano-structures. While the last aspect is ambitious, its theoretical study would already constitute a significant advance towards applications in quantum engineering.
Contact: guillaume.bachelier@neel.cnrs.fr
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Since their introduction in 1986 optical tweezers become a standard tool for non-invasive manipulation in biology, chemistry, and soft-mater physics. Nowadays, optical tweezers are widely used for trapping dielectric micro-particles or biological cells. The paramount interest of optical tweezers was underlined by the attribution of Nobel Prize in 2018 to A. Ashkin, the inventor of optical tweezers.
The first optical fiber tweezers was proposed in 1993 by A. Constable. This complementary approach shows some interesting features such as the very straightforward experimental implementation and the eased realization of counter-propagatig beam tweezers with reduced light intensities. Moreover, the optical fibers emit the trapping beam close to the trapping position. Optical aberrations are, thus, reduced, the illuminated volume is constricted, and trapping can be realized at almost any position in a complex environment such as an biological cell. high flexibility. Finally, the use of nano-structured optical fiber allows us to tailor the emitted optical beams.
At Institut Néel we are developing different optical fiber tweezers in single and dual fiber geometries and using divergent or focused beams. Our tweezers are applied to trap efficiently dielectric particles of different sizes (60 nm to 1 µm) or shapes (spheres and rods). Furthermore, the anisotropy and polarization depended emission of free, only optically trapped, rare earth-doped nanorod is studied.
In collaboration with our French and international colleagues we are currently exploring optical trapping using advanced microstructured fibers. In particular, fibers with 3D printed optical elements are showing exceptional performances to realize single fiber tweezers or trapping beams with optical angular momentum. Concerning the trapped objects, we are extending our ongoing characterization of fluorescent dielectric particles to trapping of gold nanoparticles or biologic species such as E.colie bacteria or living alga.
Please find more information on http://perso.neel.cnrs.fr/jochen.fick/
Quantum foundations and the de Broglie-Bohm interpretation: Classical/relativistic analogs of quantum physics
What does it really mean to accept standard quantum mechanics, as it is taught in textbooks, as the final words on the subject? Quantum mechanics is often considered as weird and bizarre and it is said to be unintelligible with usual classical causality and determinism in space-time. In this usual way of thinking there is no possibility to go back to the old mechanical description of Newton, Laplace or Einstein.
However, there is an elegant alternative way to describe quantum mechanics which is going back to Louis de Broglie in 1925-27 [1] and to David Bohm in 1952 [2,3] : In this interpretation particles follow well defined trajectories guided by wavefunctions, and quantum statistics are (like in classical statistical mechanics) associated with uncertainties and ignorance on the exact motions of the particles [6,7]. Furthermore, there is no genuine randomness and there is no measurement problem in this interpretation. This theory often named Bohmian mechanics (even though it should be called “de Broglian”) is empirically equivalent to the usual interpretation at least for non-relativistic quantum mechanics.
In our ongoing research we study the work of de Broglie and Bohm on several grounds :
All these exciting ongoing projects are opening new avenues for a better understanding of quantum mechanics.
Figure 2: An example [11] for a particle trajectory (black circle) driven by a complex field acting as a guiding wave function (color map). This theory is directly motivated by the old de Broglie work [1,9] on double solution and by current hydrodynamical quantum analogs projects [4].
For contacts and discussions about physics, history, and philosophy, and for applying to jobs and internships : aurelien.drezet@neel.cnrs.fr
Few general references:
[1] L. de Broglie, La mécanique ondulatoire et la structure atomique de la
matière et du rayonnement, J. Phys. Radium 8, 225-241 (1927).
[2] D. Bohm, A suggested interpretation of the quantum theory in terms of
“hidden” variables. I, Phys. Rev. 85, 166–179 (1952).
[3] A. Drezet, B. Stock, A causal and continuous interpretation of the quantum theory: About an original manuscript by David Bohm sent to Louis de Broglie in 1951, Ann. Fond. de Broglie 46, 169-195 (2021).
[4] J.W.M. Bush, A.U. Oza, Hydrodynamic quantum analogs, Rep. Prog. Phys. 84, 017001 (2020).
Our current work :
[5] A. Drezet, About Wigner Friend’s and Hardy’s paradox in a Bohmian approach: a comment of “Quantum theory cannot consistently describe the use of itself”, Int. J. Quant. Found. 5, 80-97 (2019).
[6] A. Drezet, Brownian motion in the pilot wave interpretation of de Broglie and relaxation to quantum equilibrium, Ann. Fond. de Broglie 43, 23-50 (2018).
[7] A. Drezet, Justifying Born’s rule Pα = |Ψα|2 using deterministic chaos, decoherence, and the de Broglie-Bohm quantum theory, To appear in Entropy 2021 https://arxiv.org/abs/2109.09353
[8] A. Drezet, Lorentz-Invariant, Retrocausal, and Deterministic Hidden Variables, Found. Phys. 49, 1166–1199 (2019).
[9] A. Drezet, the guidance theorem of de Broglie, Ann. Fond. de Broglie 46, 65-85 (2021).
[10] A. Drezet, P. Jamet, D. Bertschy, A. Ralko, and C. Poulain, Mechanical analog of quantum bradyons and tachyons, Phys. Rev. E 102, 052206 (2020).
[11] P. Jamet, A. Drezet, A mechanical analog of Bohr’s atom based on de Broglie’s double-solution approach, Accepted for publication in Chaos: An Interdisciplinary Journal of Nonlinear Science (2021) https://arxiv.org/abs/2106.08997
Few videos concerning our work:
https://www.youtube.com/watch?v=otqOQQQzrOs
https://www.youtube.com/watch?v=K57WwSXZCCY
Our research activities are based on the electromagnetic and mechanical properties of matter where at least one spatial dimension is reduced to a few tense nanometers and therefore rely on near-fields. This includes the study of plasmonics, with chiral/nonlinear/quantum responses, opto-mechanics from optical tweezers to macroscopic (quantum) oscillators which are coupled to light and/or spins of NV centers, nanomagnets and skyrmions. These are examples of systems that we investigate in the team by combining experiments, simulations and theoretical approaches at the forefront of the international research.
Position type: Stages Master-2 & Thèse
Contact: Jochen Fick - 0476881086 | -
Since their introduction in 1986, optical tweezers become a standard tool for non-invasive manipulation in microbiology, chemistry, and solid state physics. The importance of this device was underlined by the attribution of the Nobel Prize 2018 to Athur Ashkin, the “Inventor” of the optical tweezers. The great majority of optical tweezers are actually optimized for trapping particles in suspension, allowing for example working with biological cells such as bacteria. Optical trapping of small particles in air is a more challenging task as one has to compensate the stronger Brownian motion and consider the very strong adhesion forces of particles on a surface. Very recently we have succeed to trap efficiently sub-micron sized dielectric particles in air.
Position type: Stages Master-2 & Thèse
Contact: POULAIN Cédric -
In 1948, Hendrik Casimir predicted that quantum fluctuations of the vacuum, so-called zero-point fluctuations, could give rise to an attractive force between objects. Casimir’s calculations were idealized – he considered two perfectl conducting parallel mirrors facing each other in the vacuum at absolute-zero temperature. Since then, this prediction has been confirmed experimentally but many questions remain, among which the possibility of achieving a repulsive Casimir force.
Position type: Stages Master-2 & Thèse
Contact: POULAIN Cédric -
Quantum mechanics is well known for its apparent weirdness. But at the beginning of quantum history, the likes of Einstein, de Broglie, and later Bohm tried to decipher the meaning behind it through the use of classical analogies and mechanisms that were well understood at the time. The aim of our approach is to venture back to this lost realm of clarity in classical physics without renouncing the great achievements of modern quantum mechanics. Works by de Broglie, Bohm, and Einstein will serve as a foundation to study how some (if not all) quantum effects can be experimentally reproduced using adequately locked and fine-tuned mechanical oscillators interacting within a wavy background.
Position type: Thèses financées
Contact: Guillaume Bachelier - | Serge Huant -
Exploring new strategies for decision making is a major need in view of scaling up the capability to manage extended numbers of “bandits” (players in the theory game language), but also to deal with complex choices with an arbitrary number of outcomes. At the same time, maintaining the ability to remotely control the type of interactions among players is the cornerstone of this project. To fulfill these global challenges, all resources offered by the quantum nature of photons have to be exploited: coherence (allowing correlated responses among players), quantum superposition (providing unique properties driving the player choices), and all degrees of freedom associated with mass-less particles (scaling the available phase space). In this view, new aspects will be introduced in decision-making strategies: (i) photons multiplets will be generated for emulating larger player assemblies (ii) orbital angular momenta (OAM) will widen the number of degrees of freedom (available choices) compared to polarization-based strategies, (iii) the level of discernibility will be exploited to control the coherence of the player choices and (iv) the full spectrum between factorizable states to quantum-entangled ones will select the type of rules introduced among players. For this proposal, we aim to conduct research on parallel exploration-exploitation optimization on all theoretical, numerical, and experimental fronts, expanding previous works to more “arms” (choices in the game theory language), more realistic situations and with quantitative comparison with existing conventional algorithms. Based on the fundamental quantum nature of light, this work is foreseen to bring significant advances in various domains such as resource sharing, reinforcement learning, and parallel quantum processing.
Interested candidates must apply using this website before the end of June: https://emploi.cnrs.fr/Offres/Doctorant/UPR2940-ELOBER-045/Default.aspx
Position type: Stages Master-2 & Thèse
Contact: POULAIN Cédric - 06 12 06 29 18
Subject, available means:
In this thesis, we propose to address the Casimir effect with a hydrodynamic approach based on an acoustical analog of the quantum vacuum. Experimentally, an isotropic random acoustic noise in a liquid is used to mimic the quantum fluctuations of the vacuum Zero-point field (ZPF). The advantages of using an analog approach are manyfold: (i) fluctuation spectra can be fine-tuned and shaped at will to match that of the quantum, (ii) the orders of magnitude of the length-scales and forces are larger than their quantum counterparts, (iii) the experiments do not require heavy instrumentation (when compared with cryogenic and vacuum conditions) and (iv) most parameters can therefore easily be varied, allowing for quick exploration of any effect. Most importantly, the (acoustic) field itself can be probed and even imaged, unlike the vacuum field.
Person in charge: Benjamin PIGEAU
Permanents
Students & Post-docs & CDD
Guillaume BACHELIER
Personnel Chercheur - UGA
guillaume.bachelier@neel.cnrs.fr
Phone: 04 56 38 71 46
Office: D-411
Cathy GELLENONCOURT
Personnel Chercheur - CNRS
cathy.gellenoncourt@neel.cnrs.fr
Office: F-323
Referent: Cédric POULAIN
Clément GOURIOU
Personnel Chercheur - UGA
Office: D-216
Referent: Olivier ARCIZET
Philip HERINGLAKE
Personnel Chercheur - CNRS
philip.heringlake@neel.cnrs.fr
Phone: 04 76 88 74 73
Office: D-419
Referent: Olivier ARCIZET
Jonathan LAURENT
Personnel Chercheur - CNRS
Phone: 04 76 88 70 16
Office: D-308
Referent: Guillaume BACHELIER
Thomas LEPOITTEVIN
Personnel Technique - CNRS
thomas.lepoittevin@neel.cnrs.fr
Phone: 04 76 88 12 43
Office: K-203
Referent: Olivier ARCIZET
Luis-Paulino RODRIGUEZ-SANCHEZ
Personnel Chercheur - CNRS
luis-paulino.rodriguez-sanchez@neel.cnrs.fr
Referent: Aurélien DREZET