[Lex Computer & Tech Group/LCTG] An "ultimate take" on Young's Double Slit Experiment

Tue Jul 29 13:30:54 PDT 2025

All,

For any of you who viewed last Wednesday's talk on the EHT introduced by
Young's 1801 "Double Slit Interference Experiment"

Wolfgang Kettle's Group at MIT offers perhaps the ultimate distillation --
down to the atomic level:

The MIT News reports:

Famous double-slit experiment holds up when stripped to its quantum
essentials
MIT physicists confirm that, like Superman, light has two identities that
are impossible to see at once.
Jennifer Chu | MIT News
Publication Date:
July 28, 2025
[image: image.png]
What we have done can be regarded as a new variant to the double-slit
experiment,” Wolfgang Ketterle says, pictured with members of the MIT team.
Front, left to right: Yoo Kyung Lee and Hanzhen Lin. Back: Jiahao Lyu,
Yu-Kun Lu, Wolfgang Ketterle, and Vitaly Fedoseev.
Credits:Credit: Courtesy of the researchers
[image: image.png]
Schematic of the MIT experiment: Two single atoms floating in a vacuum
chamber are illuminated by a laser beam and act as the two slits. The
interference of the scattered light is recorded with a highly sensitive
camera depicted as a screen. Incoherent light appears as background and
implies that the photon has acted as a particle passing only through one
slit.
Credits:
Credit: Courtesy of the researchers

All,

For any of you who viewed last Wednesday's talk on the EHT introduced by
Young's 1801 "Double Slit Interference Experiment"

Wolfgang Kettle's Group at MIT offers perhaps the ultimate distillation

The MIT News reports:

*Famous double-slit experiment holds up when stripped to its quantum
essentials*

MIT physicists confirm that, like Superman, light has two identities that
are impossible to see at once.

Jennifer Chu | MIT News

Publication Date:

July 28, 2025

What we have done can be regarded as a new variant to the double-slit
experiment,” Wolfgang Ketterle says, pictured with members of the MIT team.
Front, left to right: Yoo Kyung Lee and Hanzhen Lin. Back: Jiahao Lyu,
Yu-Kun Lu, Wolfgang Ketterle, and Vitaly Fedoseev.
Credits: Courtesy of the researchers

Schematic of the MIT experiment: Two single atoms floating in a vacuum
chamber are illuminated by a laser beam and act as the two slits. The
interference of the scattered light is recorded with a highly sensitive
camera depicted as a screen. Incoherent light appears as background and
implies that the photon has acted as a particle passing only through one
slit.

Credits: Courtesy of the researchers

MIT physicists have performed an idealized version of one of the most
famous experiments in quantum physics. Their findings demonstrate, with
atomic-level precision, the dual yet evasive nature of light. They also
happen to confirm that Albert Einstein was wrong about this particular
quantum scenario.

The experiment in question is the double-slit experiment
<https://en.wikipedia.org/wiki/Double-slit_experiment>, which was first
performed in 1801 by the British scholar Thomas Young to show how light
behaves as a wave. Today, with the formulation of quantum mechanics, the
double-slit experiment is now known for its surprisingly simple
demonstration of a head-scratching reality: that light exists as both a
particle and a wave. Stranger still, this duality cannot be simultaneously
observed. Seeing light in the form of particles instantly obscures its
wave-like nature, and vice versa.

The original experiment involved shining a beam of light through two
parallel slits in a screen and observing the pattern that formed on a
second, faraway screen. One might expect to see two overlapping spots of
light, which would imply that light exists as particles, a.k.a. photons,
like paintballs that follow a direct path. But instead, the light produces
alternating bright and dark stripes on the screen, in an interference
pattern similar to what happens when two ripples in a pond meet. This
suggests light behaves as a wave. Even weirder, when one tries to measure
which slit the light is traveling through, the light suddenly behaves as
particles and the interference pattern disappears...

Nearly a century ago, the experiment was at the center of a friendly debate
between physicists Albert Einstein and Niels Bohr. In 1927, Einstein argued
that a photon particle should pass through just one of the two slits and in
the process generate a slight force on that slit, like a bird rustling a
leaf as it flies by. He proposed that one could detect such a force while
also observing an interference pattern, thereby catching light’s particle
and wave nature at the same time. In response, Bohr applied the quantum
mechanical uncertainty principle and showed that the detection of the
photon’s path would wash out the interference pattern.

Scientists have since carried out multiple versions of the double-slit
experiment, and they have all, to various degrees, confirmed the validity
of the quantum theory formulated by Bohr. Now, MIT physicists have
performed the most “idealized” version of the double-slit experiment to
date. Their version strips down the experiment to its quantum essentials.
They used individual atoms as slits, and used weak beams of light so that
each atom scattered at most one photon. By preparing the atoms in different
quantum states, they were able to modify what information the atoms
obtained about the path of the photons. The researchers thus confirmed the
predictions of quantum theory: The more information was obtained about the
path (i.e. the particle nature) of light, the lower the visibility of the
interference pattern was.

Note that there is a more physicist like report available [but you might
have to purchase it from AIP]:

*Coherent and Incoherent Light Scattering by Single-Atom Wave Packets*

Vitaly Fedoseev
<https://journals.aps.org/search/field/author/Vitaly%20Fedoseev>*, Hanzhen
Lin (林翰桢)
<https://journals.aps.org/search/field/author/Hanzhen%20Lin%20%E6%9E%97%E7%BF%B0%E6%A1%A2>
*, Yu-Kun Lu <https://journals.aps.org/search/field/author/Yu-Kun%20Lu>*, Yoo
Kyung Lee <https://journals.aps.org/search/field/author/Yoo%20Kyung%20Lee>*
, Jiahao Lyu <https://journals.aps.org/search/field/author/Jiahao%20Lyu>*,
and Wolfgang Ketterle
<https://journals.aps.org/search/field/author/Wolfgang%20Ketterle>

Phys. Rev. Lett. 135, 043601 – Published 22 July, 2025

DOI: https://doi.org/10.1103/zwhd-1k2t

Abstract

We study light scattering of atomic wave packets in free space and discuss
the results in terms of atom-photon entanglement and which-way information.
Using ultracold atoms released from an optical lattice, we realize a
Gedanken experiment which interferes single photons scattering off of
Heisenberg uncertainty-limited wave packets. We unify the free-space and
trapped-atom pictures by measuring the light scattered before and during
wave packet expansion and show the coherence properties of the scattered
light are independent of the presence of the trap. Therefore, recoilless
scattering in a trap (Mössbauer effect), the different frequency of
sidebands, and the excitation of an excited harmonic oscillator state are
not essential to the question of which fraction of light scattering is
coherent or incoherent. Our experiment demonstrates the potential of using
atomic Mott insulators to create single-atom wave packets for fundamental
studies.

Alternative version available without a paywall [may not be identical [but
then that’s the qm aspect]:

https://arxiv.org/abs/2410.19671

Anyway – this will be included in the material to be sent to LCTG to
accompany the talk

Ted

https://news.mit.edu/2025/famous-double-slit-experiment-holds-when-stripped-to-quantum-essentials-0728
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