The Hanbury–Brown Twiss effect (HBTe). Just turned seventy.
Old-school optics? Not quite.
Still sparking curiosity – if you don’t take it for granted.
It’s not about wave interference, but intensity interference.
Sounds outrageous?
It’s actually one of the cleanest windows into a mind-bending, hard-to-grasp truth about the quantum – something only a physics experiment can uncover.
So, let’s rewind.
Strangely enough, sound –not light– can help demystify it.
In short?
HBTe, now with vibes. Literally.
Too good to be true?
Well, you have to see it to believe it.
Thanks to free-space ultrasound phononics, it’s finally doable.
Now we’re talking.
The beauty of ultrasound? It’s familiar.
Better yet, cheap.
Best of all? Controllable. Even friendly.
Here’s the kicker:
Airborne ultrasound HBTe? No one’s tried it – until now.
Even luckier? No fancy setup required.
Off-the-shelf lab parts will do.
You could start building today.
Speakers. Microphones. A couple of linear stages, maybe.
A waveform generator and digital delay unit to tweak the phase – definitely helpful.
A microcontroller handles the signals.
A laptop runs the show via serial port.
Python? Your new best friend.
All of it fits on a tabletop.
Tempted?
Hold up. First things first.
You’ll need to sort out the which-path diagrams before hitting ”go.”
Still unsure if it’s legit to talk about phonons using airborne ultrasound?
Don’t sweat it. It’s sound science.
Here’s what you do:
Launch and collect ultrasonic pulses – anywhere and everywhere.
Map your data, sort it, sum it.
That’s basically it.
But wait – here’s the catch.
The first-order fringes won’t go away. Why?
Your ultrasonic waves are just too coherent.
They drown out the second-order fringes you really want.
Time to intervene.
Luckily, phase is your friend.
A smart twist –literally– can save the day.
Rotate the relative phase ∆ϕ by 2π and boom: the unwanted ∆ϕ-sensitive terms cancel out.
Decoherence – spoofed.
Unlike light, sound plays along.
Thanks to this clever hack, the real intensity fringes – two-phonon interference
– can finally emerge.
Visibility? Right on target: 50%.
And the physics payoff? Huge.
Probing hidden paths, for starters.
Opening the door to clear-cut multiparticle interference – not just with phonons or photons, but beyond.
Up next? Fluid, solid…it’s your call.
Happy ultrasonic phononics!

(Written by S. Fukatsu on behalf of all authors.)

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