AWS buys before it tries with quantum networking center Nothing in the quantum hardware world is fully cooked yet, but quantum computing is quite a bit further along than quantum networking – an esoteric but potentially significant technology area, particularly for ultra-secure transactions. Amazon Web Services is among those working to bring quantum connectivity from the lab to the …
Well their range currently seems to be about 16 billion light-years. I'd say that's not too shabby.
They're also used in oceanic fiber lines, which span several thousand kilometers and are multiplexed to the max, so it's not the photons that are the problem.
Entangled photons, well that's another subject. And a quantum network is going to have to work with switches and other networking gear I don't even know about, so that's very likely going to be an issue.
But a photon's range is until it hits an obstacle, however distant.
Not really entanglement, more "measuring determines the photon's state, so if a man-in-the-middle measures it, the end point can tell the traffic was looked at".
To send the light long distances, losses have to be accounted for, so a repeater is needed. The repeater "measures" and "resends" the signal, so that counts as "measuring" for this purpose. If ever they invented a repeater that didn't count as measuring, your attacker could use that too, and, if their system actually worked, then so would his attack.
Entanglement: well two photons, P1 and P2 are measured by two detectors D1 and D2. D1 measures P1 and D2 measures P2.
Entangle P1 and P2 via some interactions (e.g. emitting by the same regular crystal in the same state, at the same time). Measure P1 with D1, and P2 with D2, and their propeties do NOT correlate. However filter for some of the properties being the same, aka "successful entanglement", and the remaining properties are the same. As if, by magic, the act of measuring those properties of P1 with D1 sets those properties of P2 to be the same as P1, [but only for the particular subset you filtered for].
A magical effect across space, and even apparently reaching backwards in time in some experiments, as you "measure" the photon.
Well either that or some really simple thing is happening there. Something dull. Either the magic thing, or the other thing, the dull thing, is happening there.
This Quantum key exchange, it needs the magical thing.
Photon P1, interacts with matter detector D1.
Red shift occurs, D1 detected red shifted photon P1. Yet the velocity of D1 is negligable relative to the velocity of P1, so D1 must have an oscillation component in the same direction as D1/P1 is, and the apparent frequency of light must be sort of net effect of detector oscillation and photon oscillation.
Photon P2 strikes detector D1, but P2 arrives from a different direction, yet red/blue shift still occurs at D1. Hence there must also be an oscillation component of D1 in the direction of D1/P2 as well as the component in D1/P1.
But an oscillation in the plane of P2's direction, is a polarization in the plane of P1's photon. So polarization in P1 must also be a NET EFFECT of D1 and P1. Even if P1 had no oscillation in the direction of P2, D1 still does, so P1 still would have a polarization.
Now repeat for P3, arriving from a different direction to P1 and P2 at D1, same thing... another D1 component in a different direction. Now we have *two* axis polarization in D1, i.e. two components across D1/P1 axis, a circular polarization component in P1 if you prefer, so circular polarization must be a net effect of P1 and D1 too.
Now repeat for P4, a new photon arriving at D1 from a different direction to P1, P2 and P3.... same thing as before, there must be a component in that P4/D1 axis too, and relative to P1 we now have 3 components.
Now we have a three axis waddle, brilliant, you can do motion with a 3 axis waddle! It cannot be perfectly straight, but who would know if the curve is small, and 'velocities' are always really low (~>0 wavelengths per oscillation of the field, the speed of matter), or very high (<~1 wavelength per oscillation of the field, the speed of light). Sure your motion will always have a slight curve, your universe must be curved and finite and all.... but it's velocity to the person with nothing straighter to compare it against. Again the components are net effects, so such a waddle is a NET effect.
[Here I'm pointing you to the mechanism of motion, the thing that gives light its motion, matter its scale and is the basis for velocity. Given you or I can make a waddle across that 3 component field, an you have those components to make that motion, where is the motion if it isn't velocity!]
So you have 'entangled' two photons P1 and P2. And you imagine all those properties are carried completely by the photons. Yet the above tells you that they are all NET effects, spin, polarization even velocity, all net effects of the detector and photon.
Now you run an entanglement experiment:
P1 is measured by detector D1, and P2 by detector D2.
You measure properties net(P1,D1), and compare it to properties net(P2,D2). You "entangled" P1 and P2, perhaps they were emitted by the same event in the same matter at the same time, so you imagine their properties should be the same, but they are not. You forgot about D1 and D2. To measure net(P1,D1) as the same as net(P2,D2), you have to ensure that those base oscillation of D1 is the same as D2's.
Since all your complex properties derive from much simpler oscillations base properties, if the base properties of net(P1,D1), are the same as Net(P2,D2) then all the more complex properties will also be the same.
Hence you filter for "successful entanglement" either directly (by filtering for similar derived properties), or indirectly (a 'coincidence circuit' that you adjust the spacing of your experiment till you get more entanglement).
Do that, and now, as if by magic all the properties correlate. It's almost as if the act of measuring the property, set the property, and the universe adjusted itself to compensate for your measurement!
It's not that you "measure" the photon's properties and set those properties by the act of measuring. You filtered for the NET properties. So quantum crypto key exchange cannot work. Your attacker does not set the photon's properties by measuring them.
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