Journée "Fondements de
la physique quantique"
Discussion Day "Foundations of Quantum Physics"
Final Programme Final

28 / 08 / 2017, UTT Troyes 
9h15
Accueil  Welcome
(café et croissants)
9h40
Ouverture
Opening
Amphi
N101 Lecture Hall
9h45
Philippe Grangier
Recovering the quantum formalism
from physically realist axioms Abstract
10h30
Aurélien Drezet
De Broglie
pilotwave theory and randomness Abstract
11h15
Michel Bitbol
Quantum
physics in the first person, present tense Abstract
12h
Déjeuner (sur place)
Lunch (on site)
13h
Jean Bricmont
What does it mean to measure an
operator? Abstract
13h45
Thomas Durt
Interaction between
two walkers and de Broglie double solution Abstract
14h30
Alexandre Gondran
The de BroglieBohm weak
interpretation and the theory of double preparation
Abstract
15h15
Pause Café
Coffee Break
15h30
Thomas Kauten
Experimental measurements of
bounds on higherorder interferences Abstract
16h15
Alex Matzkin
Can the
properties of a quantum system vanish ? Abstract
17h
Discussion
Remarques finales
Final Remarks

Résumés / Abstracts 
Quantum physics
in the first person, present tense (Michel Bitbol) Does Quantum Physics offer a (complete or
incomplete) representation of the “real world out there”? A
powerful critique of the representational conception of
knowledge has been formulated in biology by the autopoietic
theory of living beings, in the cognitive science by the theory
of enaction, and in philosophy by phenomenology. These three
disciplines approach knowledge from the standpoint of the
knower, namely in the first person. And they show how the
illusion of a representation is generated by the process of
anticipation and adaptation of the knower that stands for
“knowledge”. Quantum physics might well be a case wherein the
classical representational conception of knowledge has been
defeated, and the firstperson foundation of knowledge has been
laid bare. This was already suggested by Bohr, and more
explicitly claimed by several contemporary physicists, such as
David Mermin and Christopher Fuchs in their “QBist”
interpretation of quantum physics. Here, I will show that an
extreme firstpersonal conception of quantum knowledge (not only
from the standpoint of the knower, but rather from the
standpoint of her present state), easily makes sense of standard
“paradoxes” of quantum physics. It also accommodates
effortlessly the nonstandard uses of “generalized quantum
theory” in the human sciences.
What does it
mean to measure an operator? (Jean Bricmont)
The usual calculus of state
vectors and operators is perfectly able to predict
accurately « results of measurement » of quantum
« observables » represented by operators.
But what do these measurements really measure? The naive
view is that they measure preexisting properties of the
quantum objects, but this view is rendered untenable by the
no hidden variable theorems of Bell and KochenSpecker.
We will explain how the de
BroglieBohm theory gives a meaning to those
« measurements », that do not, in general, measure
any preexisting properties of the quantum objects but
are genuine interactions between the quantum object and the
measuring device. This vindicates the intuition of Bohr and
others about the quantum object and the measuring device
forming an inseparable whole, but this idea follows here
from the equations of the de BroglieBohm theory and not
from some philosophical a priori.
De Broglie pilotwave theory and randomness (Aurélien
Drezet) During this talk we will review a old
and serious problem of the standard de BroglieBohm approach
which is how to justify the probability rules of quantum
mechanics (the so called Born's rule) from a purely
deterministic dynamics.
Interaction
between two walkers and de Broglie double solution (Thomas
Durt)
Recently*, we elaborated a theoretical model according to
which elementary particles and/or droplets are represented
by solitonic solutions of a nonlinear equation, in the mind of
de Broglie's double solution program**. The essential
ingredient of our model is the factorisation ansatz according to
which the wave describing the walker (and/or particle) and
its environment factorizes into the product of a pilot wave
associated to the environment with a peaked solitonic wave
associated to the walker (and/or particle). This model
originally aimed at describing elementary particles, but it
appeared that it could also be applied in order to
describe the phenomenology of walkers*,**. In the case of
elementary particles, our model allowed us to predict the
appearance of a pseudogravitational interaction similar
to Newton's gravity. In the case of droplets, we predicted
that the interaction potential between two droplets is
proportional to the Helmholtz Green function, which
implies that attractive and repulsive interactions are
present, which appeared to provide a good agreement with
the experimental observations*. Memory also plays a role in
our approach because we showed** that in order to satisfy
the de BroglieBohm guidance equation, it is
necessary that the intrinsic movement of the soliton
possesses a stochastic contribution (in agreement with what de
Broglie called the ``hidden thermostat'' hypothesis) a
possibility explored in the 50's by Bohm and Vigier. The scope
of our talk is to provide a survey of these ideas and to
briefly address some open questions like e.g. ``Is it correct
to describe a bouncing droplet by a soliton?'', ``How to
falsify experimentally our model?'', or ``To which extent
is it necessary to invoke quantum mechanics in this
approach?'' and so on.
*T. Durt, Generalized guidance equation for peaked quantum
solutons and effective gravity, EPL 114 (2016) 10004.
**L. de Broglie's double solution and selfgravitation, Annales
de la Fondation Louis de Broglie, Volume 42, special issue
(2017) 43, http://aflb.ensmp.fr/AFLB421/table421.htm.
The de BroglieBohm
weak interpretation and the theory of double preparation
(Alexandre and Michel Gondran) When at the Solvay congress of
1927, Louis de Broglie proposed the pilot wave instead
of the theory of the double solution which he sought to
develop, it is for him only a secondbest. Considering
Bernard d 'Espagnat' s profound remark that the mathematical
formalism of quantum mechanics "is entirely based on the
preparation of systems and the measurement of observables" ,
we propose an interpretation of the wave function which
depends on the preparation of the quantum system and which
illuminates the formidable intuition of de Broglie.
If the theory of the pilot wave is restricted to free or
unbounded particles whose wave function can be described in
threedimensional space, we can show the continuity with the
classical mechanics for particles prepared in the same way,
since the energy spectrum of quantum particles is in this case
continuous as in classical mechanics. Theoretically, we prove
, when the Planck constant h tends to 0, that the
density and phase of the wave function of a particle (of
a set of identical particles without interaction) converge
towards HamiltonJacobi's density and action of a set of
unrecognized prepared classical particles which verify the
HamiltonJacobi statistical equations.
As the HamiltonJacobi action pilots the point particle in
classical mechanics, by continuity, it is legitimate that the
phase pilots the point quantum particle. We call dBB weak
interpretation the restriction of the pilot wave to the
case of identical particles without interaction. This
interpretation extends to the particles entangled by the spin
as we have shown for the EPRB experiment. In practice, it is
the positions of the mass particles that are the directly
measured variables, the others being deduced by the theory.
For the other bounded quantum systems whose wave function is
defined in a 3Ndimensional configuration space (entanglement
by positions and moments), we propose an interpretation which
generalizes the soliton wave presented by Schrödinger in 1926
and which corresponds to the coherent state of the harmonic
oscillator. The quantum particle is then extended and the wave
function represents completely the particle as in the
Copenhagen interpretation. This interpretation also
extends to particles intanglement by the spin, which
explains the success of DFTbased calculation methods.
Refs.
M. Gondran et A. Gondran, A synthetic interpretation: the
doublepreparation theory,Phys. Scr. T163 (2014) 014029.
M. Gondran et A. Gondran, Replacing the singlet spinor of the
EPRB experiment in the Configuration Space with Two
SingleParticle Spinors in Physical space. Foundations of
Physics, 46(9): 11091126, 2016.
Recovering the quantum
formalism from physically realist axioms
(Philippe Grangier and Alexia Auffèves). We present a heuristic
derivation of Born's rule and unitary transforms in
Quantum Mechanics, from a simple set of axioms built
upon a physical phenomenology of quantization [1, 2].
This approach naturally leads to the usual quantum
formalism, within a new realistic conceptual framework
that is discussed in details. Physically, the
structure of Quantum Mechanics appears as a result of
the interplay between the quantized number of
"modalities" accessible to a quantum system, and the
continuum of "contexts" that are required to define
these modalities. Mathematically, the Hilbert space
structure appears as a consequence of a specific
"extracontextuality" of modalities, closely related
to the hypothesis of Gleason's theorem, and consistent
with its conclusions.
Refs.
[1] A. Auffeves and P. Grangier, Found. Phys. 46, 121
(2016) https://arXiv.org/abs/1409.2120
[2] A. Auffeves and P. Grangier, Sci. Rep. 7, 43365
(2017) https://arXiv.org/abs/1610.06164.
Experimental measurements of
bounds on higherorder interferences (Thomas Kauten)
Thomas Kauten, Robert Keil, Thomas Kaufmann, Benedikt
Pressl, Sebastian Gstir, Christoph Dittel, Rene Heilmann, Toni
Eichelkraut, Alexander Szameit, Caslav Brukner & Gregor
Weihs
Quantum mechanics is a fundamental theory to describe the
physics of microscopic objects, but there are still questions
whether this theory is complete or not. If the answer to this
question is no, axioms could be violated. One of the fundamental
axioms of quantum mechanics is Born’s rule, which claims that
the description of nature is probabilistic, i.e. P(r,t) =
Ψ(r,t)2. Combined with the quantum mechanical superposition of
wavefunctions this results in interference terms, which contain
all the possible pairings of the states in the superposition,
but do not allow higherorder interference terms with more than
two constituents.
In this work, we will present results of improved versions of an
experiment, which was proposed by Sorkin in 1994 [1], and was
experimentally implemented for the first time in 2010 [2], with
the goal of putting a bound on the potential magnitude of
higherorder interference terms. For this we employed different
types of switchable multipath interferometers (a freespace
bulk optical [3], a hybrid bulkintegrated [4] and a fully
integrated interferometer) in different measurement regimes
(classical, semiclassical and quantum). Improved power and
phase stabilization and increased throughput enables us to
provide an upper bound on the potential magnitude of these
higher order interference terms which is two orders of magnitude
smaller compared to previous works [5]. The discussion of our
experiment also contains the characterization and compensation
of systematical errors in our measurement setup, such as the
detector nonlinearity [6]. Additionally, we will use our
integrated interferometers in the future to test for the
possibility of quantum mechanical wavefunctions based on
quaternions or octonions rather than complex numbers [7].
Our experiments confirm quantum mechanics by ruling out higher
order interference terms to an extent that is more than four
orders of magnitude smaller than the expected pair wise
interference.
Refs.
[1] R. D. Sorkin, “Quantum mechanics as quantum measure theory”,
Mod. Phys. Lett. A 9, 31193128 (1994).
[2] U. Sinha, C. Couteau, T. Jennewein, R. Laflamme, and G.
Weihs, “Ruling Out MutiOrder Interference in Quantum
Mechanics”, Science 329, 418421 (2010).
[3] T. Kauten, R. Keil, T. Kaufmann, B. Pressl, C. Brukner, and
G. Weihs, “Obtaining tight bounds on higherorder interferences
with a 5path interferometer”. New J. Phys., 19, 033017 (2017).
[4] R. Keil, T. Kaufmann, T. Kauten, S. Gstir, C. Dittel, R.
Heilmann, A. Szameit, and G. Weihs, “Hybrid waveguidebulk
multipath interferometer with switchable amplitude and phase”.
APL Photonics, 1, 081302 (2016).
[5] I. Söllner, B. Gschösser, P. Mai, B. Pressl, Z. Vörös, and
G. Weihs, “Testing Borns Rule in Quantum Mechanics for Three
Mutually Exclusive Events”, Found. Phys. 42, 742751 (2012).
[6] T. Kauten, B. Pressl, T. Kaufmann, and G. Weihs,
“Measurement and modeling of the nonlinearity of photovoltaic
and Geigermode photodiodes”, Rev. Sci. Instrum. 85, 063102
(2014).
[7] A. Peres, “Proposed Test for Complex versus Quaternion
Quantum Theory”, Phys. Rev. Lett. 42, 683686 (1979).
Can the
properties of a quantum system vanish ? (Alex Matzkin)
The Weak Measurements approach is a framework based on
implementing nondestructive, nonperturbing measurements on
a quantum system as the system evolves from an initially
prepared state to a final state obtained by performing a
standard measurement. The result of a weak measurement is
called the “weak value” of the weakly measured observable.
Weak values have peculiar features. In particular, a
vanishing weak value means that the corresponding system
property cannot be found at the location where the
observable was weakly measured. This may have striking
consequences, like not being able to detect a particle
inside an interferometer although it went in and out, or
observing a spatial separation between a particle and one of
its properties. I will describe situations in which quantum
properties appear to “vanish” and I will put forward an
explanation based on the analysis of null weak values.
Refs.
Q. Duprey and A. Matzkin Phys. Rev. A 95, 032110 (2017)
Q. Duprey, S. Kanjilal, U. Sinha, D. Home and A. Matzkin,
arXiv:1703.02959 (2017)