Entangled Photons Maintained Under New York Streets

https://physics.aps.org/articles/v17/125

by lc0_stein • 2 years ago

91 35 2 years ago

physics.aps.org

Interesting, a sort of quantum eruv https://en.wikipedia.org/wiki/Eruv

Does anyone have any additional context on the throughput numbers? It says 20k photons per second at 99% fidelity and 500k at 90%, but what is the actual bandwidth needed for reasonable usage / computation?

golergka• 2 years ago

In addition, it is also forbidden to transfer an object for a distance of 4 cubits

This gave me pause.

ars2• 2 years ago

In a public area you can not transport objects, the intention being that the Sabbath is a day of rest, and you should stay home or at least near your home and not do work.

Note: Jewish law very carefully defines "public area", and it would take several pages of text to fully explain it, so before objecting be aware you may be lacking background knowledge.

tapotatonumber9• 2 years ago

Not 4 qubits?

ars2• 2 years ago

20k (10^4) photons/sec is a TINY amount.

An ordinary flashlight emits something like 10^18 photons per second. Even a star in the night sky sends around 10^8 to your eye.

That few photons is not going to have much bandwidth.

asplake• 2 years ago

They’re measuring individual photons, right? I’m old enough to remember modems slower than that. No doubt they will get faster, but what if they were used only for (say) key exchange?

krastanov• 2 years ago

"20k photons at 99% fidelity" usually means "we can detect each of these 20k photons separately with 1% error rate", which would be roughly 20kb/s. Low bandwidth, but it has little to do with how much light comes from a flash light or from the night sky, because they are using detectors that detect each photon (as opposed our eyes or typical network equipment which might need a large average number of photons per bit).

jerf• 2 years ago

AIUI, this sort of system is likely to end up a lot like TLS negotiation and asymmetric crypto in general. Even if it never has very much bandwidth, the ability to share secrets on a channel that is not just declared secure by engineers, but declared secure by physics has some advantages. Asymmetric crypto is generally atrociously slow too, but incredible useful because we can use it to bootstrap symmetric crypto which is very fast.

Of course, if it does upgrade to the point that it can move gigabits per second, they'll use it for that. I don't know of a particular reason why this would be fundamentally impossible. I'm just saying that's not a necessary condition for the technology to be useful.

ishtanbul2• 2 years ago

This is great but why can’t i get fiber internet in my bk apartment. Still struggling with spectrum coaxial pulling less than 5mbps today. No options on my block. Sheesh

bqmjjx0kac• 2 years ago

Find a new apartment? Here's the FCC broadband map: https://broadbandmap.fcc.gov/home

pokepim• 2 years ago

Is this solution to every issue in the US? Like if something is shit then instead of fixing just run from the problem? I guess that’s why you are stuck choosing between republicans and democrats every 4 years lol.

rockskon2• 2 years ago

Doesn't that map consider an entire region serviced if a single residence in that entire region can get the advertised speeds?

ishtanbul2• 2 years ago

that map is a great resource, thank you

dudeinjapan• 2 years ago

I knew those turtles were up to something!

bloomingeek• 2 years ago

Damn, you got there before me!

mjklin• 2 years ago

Everything was fine with our entangled photon system until the power grid was shut off by d*ckless here

LgWoodenBadger• 2 years ago

How does one detect whether a pair is still entangled?

AlecBG• 2 years ago

I don't know how they did it, but verifying Bells inequality would do it if you made many pairs

rdtsc2• 2 years ago

Easy-peasy. They will periodically see if the photons, when measured had already been measured by an eavesdropper. In quantum world measurement will affect the entangled system, so it’s impossible for someone to measure (read) the data in between without it being detected at both ends.

renox• 2 years ago

so it’s impossible for someone to measure (read) the data in between without it being detected at both ends.

You give too little information for this to be understandable.

nightowl_games• 2 years ago

I'm under the impression you can't. You create an environment that is more likely to keep the sets of particles from interacting with anything else and then you create an entangled pair. To confirm the entanglement I believe would take several measurements of several pairs of particles and these measurements would result in a probability that they were still entangled, not a certainty.

I found this explanation:

https://www.quora.com/Is-it-possible-to-detect-if-a-particle...

In my opinion, it's not the entanglement that is interesting or confusing, it's the super positions of both particles before they are measured that is hard to explain... How can two particles be in super positions of two states but then when you measure them they are always complimentary? Either it was "spooky action at a distance" ie (particle A communicated it's measurement result to particle B) or there is "hidden variables" inside the super positions that determines the result of the measurements.

geodel• 2 years ago

Perhaps by checking their Instagram status.

itishappy• 2 years ago

Check correlation via interference. They'll give consistent results if entangled, and random results if they're not.

rrnechmech• 2 years ago

There's a TMNT reference lurking here somewhere :)

Entangled Photons Maintained Under New York Streets

Related Stories