Historical research guide · 0590 · 2026

Time-Domain Perspective on Quantum Fields: Role of Indistinguishability

Gabriel Demontigny · Patrick Cusson · Andrei Rasputnyi · Stéphane Virally · Denis V. Seletskiy

In one minute

A squeezed state of light is the vacuum with its quantum jitter pushed around — quieter along one direction of the field, noisier along the other, the total never falling below what the uncertainty principle allows. Gabriel Demontigny, Patrick Cusson, Andrei Rasputnyi, Stéphane Virally and Denis Seletskiy of the femtoQ laboratory at Polytechnique Montréal take that resource into the time domain. Their subject is the two-mode squeezed state, in which one pump photon splits into twins — a signal beam and an idler beam — correlated more tightly than any classical pair of beams can be. The talk’s argument is that what you learn depends on how you look. Measure one twin and keep only the runs with a chosen outcome, and that post-selection leaves the surviving beam in a whole family of nonclassical states. Measure both twins together instead, and the pair stops behaving like two beams and shows you the structure of a single squeezed mode. The hinge between those two pictures is indistinguishability.

Connection

Chapter 2 treats the vacuum as a medium you can shape rather than an absence, and squeezed light is the cleanest laboratory handle on that shaping — you push the fluctuations from one quadrature into the other and watch where they go. Chapter 4 needs the same resource for a different reason: squeezed vacuum is, alongside the Casimir geometry, one of the two laboratory routes to a region of field energy below the ambient vacuum level that metric-engineering proposals are built on.

From the source

Two-mode squeezed states are a versatile resource. Post-selecting on the measurement of one daughter beam leaves the other daughter beam in a variety of nonclassical states, so a single source can be turned into many different quantum states of light by the choice of what you keep.Abstract, sentences 1 and 2
A joint measurement of both daughter beams, rather than a post-selection on one of them, reveals instead the structure of single-mode squeezed states. The same physical resource therefore reads out as two different objects depending on whether the two arms are measured together or separately.Abstract, final sentence
The organising idea the talk names is indistinguishability: in a time-domain description of these quantum fields, whether the two down-converted paths can in principle be told apart is what decides which of the two pictures the measurement returns.Title; CLEO 2026 session FM2F, paper FM2F.3, Long Beach, 2 to 6 May 2026
Context, from the same team’s open preprint rather than from this paper: the source behind this line of work is a bright twin-beam generator using type-0 parametric down-conversion in periodically poled lithium niobate at megahertz repetition rate, with the signal near 1.37 micrometres, the idler near 4.0 micrometres, pulses of roughly 100 femtoseconds, and a Schmidt number close to 1.05 — effectively a single spatio-temporal mode — held across several orders of magnitude of brightness.Companion preprint by the same team, arXiv 2605.15385, abstract
What to watch, and again from the laboratory’s open preprints rather than this paper: the proposal to promote electro-optic sampling into a full time-domain quantum tomography, detecting both the electric field and its Hilbert-transform quadrature so that the quasi-probability distribution of a propagating field can be reconstructed directly in time. The measurement that would settle it is a reconstructed distribution for a squeezed mid-infrared field, read within a single optical cycle.Onoe, Virally and Seletskiy, arXiv 2307.13088, abstract
The step this work does not take, and does not claim to: squeezed vacuum is a resource for regions where field energy sits below the ambient vacuum level, which is the ingredient the metric-engineering literature asks for. This paper is about producing and reading that resource cleanly in the time domain, not about applying it.Read against the abstract; no application is claimed in the paper

The way in

https://doi.org/10.1364/CLEO_FS.2026.FM2F.3

Historical source-access record. This guide links to the original; it does not reproduce the paper text.

REGISTRY CORRECTION. The corpus record labelled this item rights ’video’, which was a scraper guess from the conference format. It is not a video: it is a conference paper in the CLEO 2026 technical digest, published by Optica Publishing Group, presented in session FM2F, Ultrafast Dynamics in Quantum Light-matter Systems, as paper FM2F.3 at Long Beach, California, 2 to 6 May 2026. The Optica record was reached and read on 2026-09-08; it carries the copyright line ’© 2026 The Author(s)’ and displays no open-access or Creative Commons designation, and the full digest paper is behind the publisher’s subscription. So this sheet reproduces no text of the paper. SOURCE NOT REACHED IN FULL: the summary and the first three claims are written from the authors’ own published abstract and from the conference record — title, session, authors, affiliations — and their locators point to those. Claims four and five are context, and are labelled as such: they are read from the same laboratory’s open preprints, cited by arXiv number in the locator, not from this paper. Affiliations from the Optica record: Demontigny, Cusson, Virally and Seletskiy at Laboratoire femtoQ, Département de génie physique, Polytechnique Montréal, Québec; Rasputnyi at the Max Planck Institute for the Science of Light and Friedrich-Alexander-Universität Erlangen-Nürnberg.

How to cite it

Gabriel Demontigny, Patrick Cusson, Andrei Rasputnyi, Stéphane Virally, Denis V. Seletskiy (2026) Time-Domain Perspective on Quantum Fields: Role of Indistinguishability doi:10.1364/CLEO_FS.2026.FM2F.3

Where it sits in the curriculum

What the vacuum is