The h Bar

Emilio Pisanty

12:00 AM

Is this an actual setup with an actual radioactive source that you plan on physically implementing yourself?

heather

yes. though i don't have said radioactive source yet.

Emilio Pisanty

and, if so, do you have someone on the ground who's trained in the safe handling of that source?

heather

my dad has experience handling that stuff.

Emilio Pisanty

ok, just needed to check

heather

he said he's willing to help make sure i don't injure myself.

@EmilioPisanty no, thank you =)

so, let's see, $E=hc/\lambda$

so assuming the upper end, 10 picometers for wavelength, $E = 1.98644582 × 10^{-14 }$ joules

DanielSank

12:03 AM

That's not very many Joules.

heather

which is 123,984.197 electron volts

DanielSank

That's a lot of electron volts.

@EmilioPisanty Yeah, which is why optical quantum computing is hard.

Emilio Pisanty

@heather this may be of interest blogs.scientificamerican.com/critical-opalescence/…

heather

@EmilioPisanty thanks =) I actually had already found that, it's quite interesting.

Emilio Pisanty

@DanielSank ... and they should all quit and join the superconducting-qubit overlords? =P

DanielSank

12:04 AM

Why, yes!

heather

@EmilioPisanty so...not quite a mega electron volt.

is it high enough for it to work if enough gamma photons get to try their hand at it?

Emilio Pisanty

@heather I know the air becomes opaque at some point between near UV and vacuum UV, and it becomes transparent at some point afterwards, but I don't know what that second point is

heather

@DanielSank i've been feeling like a traitor because i'm researching optical quantum computing =P

Emilio Pisanty

I imagine MeV photons will quite happily blaze through whatever you put in front of them that isn't made of lead

DanielSank

@heather It's a good idea to learn more things.

That never a bad idea.

heather

12:08 AM

i just came across the randomest sentence in a wikipedia blurb: 'Reindeer use near-UV radiation to see polar bears [...]'

2

Emilio Pisanty

@heather btw the author of that thesis is in the bay area at the moment, and she's super awesome. If you go back to California lemme know and I'll see if she can give tours.

DanielSank

@heather Polar bears are awesome.

heather

@EmilioPisanty =O wow, okay. thank you! (i don't know if i'll be in california anytime soon, but still, that's awesome!)

DanielSank

Their hairs are like little greenhouses.

Emilio Pisanty

@DanielSank they're the same as grizzlies

DanielSank

12:11 AM

@EmilioPisanty That's not quite true.

They're not the "same".

↑ source

yah yah yah

@EmilioPisanty well, i think i'm okay in terms of photon energies/transparency, because 10 picometers is the upper limit in terms of wavelength, or the lower limit in terms of energy. They'll only be more energetic from there.

Emilio Pisanty

and yes, I'm abusing the term "same"

heather

besides, it's the least of my problems.

DanielSank

12:12 AM

10 picometers is not a lot of meters.

heather

okay, instead of interference, is there a way to measure phases of each and compare the two?

DanielSank

You wanna measure photon phases? eeeesh

heather

(i know i can compare using a two-channel oscilloscope, so i guess just measuring photon phases)

DanielSank

I have no idea how you'd use a two channel oscilloscope to measure photon phases.

heather

@DanielSank compare, not measure.

DanielSank

12:13 AM

Photon frequencies >>>> frequencies you can measure on a scope.

heather

oh.

Emilio Pisanty

@DanielSank microwaves are also photons

DanielSank

LOLOL

Ok true.

Emilio Pisanty

@heather beyond the GHz microwave regime, the only way to access phases is via interference

DanielSank

But heather was talking about gamma photons.

Emilio Pisanty

12:14 AM

I know, I know

heather

@EmilioPisanty ::groans::

DanielSank

Groan all you want. Mamma Nature don't care.

;-)

heather

@DanielSank wikipedia lied to me =/ or rather, i didn't think about how the gamma bit affects things.

Emilio Pisanty

@heather if it helps, I'm facing precisely that problem myself

heather

really?

Emilio Pisanty

12:15 AM

I have an observable that is encoded in the relative phase between a fundamental and its second harmonic

DanielSank

@EmilioPisanty What frequency range?

Emilio Pisanty

and it's... proving tricky to design a good experimental protocol for measuring it

@DanielSank honestly? I don't care

DanielSank

@EmilioPisanty Then call Michel Devoret.

Emilio Pisanty

who?

heather

okay, are there ways to make the frequencies of two photons the same?

DanielSank

12:16 AM

These guys

@heather Yeah, you need nonlinear materials.

heather

@DanielSank it just keeps coming back to these guys, doesn't it?

Emilio Pisanty

or if you're intent on using gammas, you can look for something with a double-e^+ decay

DanielSank

@EmilioPisanty The microwave quantum / superconducting qubits world has a catalog of weird mixing devices that work in the quantum regime.

0celoñe7

@DanielSank Curved swords?

heather

@EmilioPisanty not intent on using gammas, just entangled photons.

Emilio Pisanty

12:18 AM

@DanielSank to clarify, I'm interested in propagation in free space, in the linear-optics regime

DanielSank

@heather ..and I guess you don't want to use a cryostat.

@EmilioPisanty So you do care about the frequency.

heather

" In neutrinoless double beta decay, a hypothesized process that has never been observed, only electrons would be emitted."

curses.

Emilio Pisanty

@heather so the vast majority of single-photon sources use spontaneous parametric down-conversion as the key process

heather

@DanielSank not particularly.

Emilio Pisanty

@DanielSank you could do my experiment with microwaves in free space

DanielSank

12:20 AM

@EmilioPisanty yeah yeah ok fine.

Emilio Pisanty

it would have the added bonus that you could just measure the phase directly

DanielSank

true dat

Emilio Pisanty

but really, I'm looking between the near IR and the near UV, for added oomph with the optics people

DanielSank

Yeah ok. Can't help you.

Emilio Pisanty

well, luckily I work in a photonics institute ;-)

heather

12:22 AM

@EmilioPisanty so the photon pairs produced are entangled?

Emilio Pisanty

@heather exactly

heather

that sounds like another thing i want to build =)

okay, question: how expensive is the laser involved?

Emilio Pisanty

and there's probably plenty of interesting physics that an enterprising DIYer can do with that

@heather probably not very

heather

because, if it just needs to be a laser beam that produces single photons every, say, microsecond, i could do that without too much trouble

i've already done some calculations for that.

and then i can just use a mirror for the phase shift, and then i'm assuming measurement also becomes much easier...

Emilio Pisanty

I'm not sure how expensive the crystal is (and how carefully it needs to be poled for phase matching to work well) but it's probably reasonably obtainable

@heather (but again, though, making single photons interfere is not an easy experiment)

heather

12:26 AM

@EmilioPisanty, of course, but it's a lot easier with photons that aren't gamma photons.

even though i am still interested in doing that experiment.

Emilio Pisanty

@heather yes

but more importantly

if you build that setup, there's plenty of interesting optics experiments you can do that don't require single-photon conditions to work

i.e. it degrades gracefully

heather

looking it up on one supplier, it seems to be \$500-$1000 for the crystal.

Emilio Pisanty

really?

0celoñe7

Where are you gonna get that money?

I have suggestions if you need them

heather

eksmaoptics.com/nonlinear-and-laser-crystals/nonlinear-crystals/…

@0celoñe7 i'll take them =)

0celoñe7

12:28 AM

@heather Get a job

heather

that's actually easier said than done, with my dad. he's...kind of picky about what sort of job he wants me to have.

i've been trying to find some sort of programming job, because that'd make him happy, or a job putting papers into LaTeX, but all freelancing sites I've checked are for 16 and up or 18 and up

eh, well, i'll figure out a way.

DanielSank

I think my first jobs were mowing lawns, babysitting, and swim lessons.

heather

hmm, it seems i'll need a specific type of laser as well.

oh, looks like i can get it for $40-ish dollars.

@EmilioPisanty if one hasn't been manipulated at all, and one's phase has been manipulated, what type would that be?

i think it'd be temporal coherence, because spatial coherence seems to be checking whether the amplitudes are the same.

and, i believe the interferometer to use would be the mach-zender, as wikipedia says "The interferometer has been used, among other things, to measure phase shifts between the two beams"