Two atoms entangled using microwaves for the first time

Aug 10, 2011
This is a composite photo of microwave apparatus used in NIST quantum computing experiments. A pair of ions (electrically charged atoms) are trapped by electric fields and manipulated with microwaves inside a glass chamber at the center of the apparatus. The chamber is illuminated by a green light-emitting diode for visual effect. An ultraviolet laser beam used to cool the ions and detect their quantum state is colorized to appear blue. (Y. Colombe/NIST)

Physicists at the National Institute of Standards and Technology have for the first time linked the quantum properties of two separated ions (electrically charged atoms) by manipulating them with microwaves instead of the usual laser beams, suggesting it may be possible to replace an exotic room-sized quantum computing "laser park" with miniaturized, commercial microwave technology similar to that used in smart phones.

Microwaves, the carrier of wireless communications, have been used in past experiments to manipulate single ions. But the NIST group is the first to position microwaves sources close enough to the ions—just 30 micrometers away—and create the conditions enabling entanglement, a quantum phenomenon expected to be crucial for transporting information and correcting errors in quantum computers.

Described in the August 11 issue of Nature, the experiments integrate wiring for microwave sources directly on a chip-sized ion trap and use a desktop-scale table of lasers, mirrors, and lenses that is only about one-tenth of the size previously required. Low-power ultraviolet lasers are still needed to cool the ions and observe experimental results but might eventually be made as small as those in portable DVD players. Compared to complex, expensive laser sources, microwave components could be expanded and upgraded more easily to build practical systems of thousands of ions for and simulations.

"It's conceivable a modest-sized quantum computer could eventually look like a smart phone combined with a laser pointer-like device, while sophisticated machines might have an overall footprint comparable to a regular desktop PC," says NIST physicist Dietrich Leibfried, a co-author of the new paper.

"Although quantum computers are not thought of as convenience devices that everybody wants to carry around, they could use microwave electronics similar to what is used in smart phones. These components are well developed for a mass market to support innovation and reduce costs. The prospect excites us."

Quantum computers would harness the unusual rules of quantum physics to solve certain problems—such as breaking today's most widely used data encryption codes—that are currently intractable even with supercomputers. A nearer-term goal is to design quantum simulations of important scientific problems, to explore quantum mysteries such as high-temperature superconductivity, the disappearance of electrical resistance in certain materials when sufficiently chilled.

Ions are a leading candidate for use as quantum bits (qubits) to hold information in a quantum computer. Although other promising candidates for qubits—notably superconducting circuits, or "artificial "—are manipulated on chips with microwaves, ion qubits are at a more advanced stage experimentally in that more ions can be controlled with better accuracy and less loss of information.

The same NIST research group previously used ions and lasers to demonstrate many basic components and processes for a quantum computer. In the latest experiments, the NIST team used microwaves to rotate the "spins" of individual magnesium ions and entangle the spins of a pair of ions. This is a "universal" set of quantum logic operations because rotations and entanglement can be combined in sequence to perform any calculation allowed by quantum mechanics, Leibfried says.

In the experiments, the two ions were held by electromagnetic fields, hovering above an ion trap chip consisting of gold electrodes electroplated onto an aluminum nitride backing. Some of the electrodes were activated to create pulses of oscillating microwave radiation around the ions. Radiation frequencies are in the 1 to 2 gigahertz range. The microwaves produce magnetic fields used to rotate the ions' spins, which can be thought of as tiny bar magnets pointing in different directions. The orientation of these tiny bar magnets is one of the quantum properties used to represent information.

Scientists entangled the ions by adapting a technique they first developed with lasers. If the microwaves' magnetic fields gradually increase across the ions in just the right way, the ions' motion can be excited depending on the spin orientations, and the spins can become entangled in the process. Scientists had to find the right combination of settings in the three electrodes that provided the optimal change in the oscillating magnetic fields across the extent of the ions' motion while minimizing other, unwanted effects. The properties of the entangled ions are linked, such that a measurement of one ion would reveal the state of the other.

The use of reduces errors introduced by instabilities in laser beam pointing and power as well as laser-induced spontaneous emissions by the . However, microwave operations need to be improved to enable practical computations or simulations. The NIST researchers achieved entanglement 76 percent of the time, well above the minimum threshold of 50 percent defining the onset of , but not yet competitive with the best laser-controlled operations at 99.3 percent.

In addition to improving microwave operations by reducing unwanted ion motion, the NIST team also plans to study how to suppress cross-talk between different information processing zones on the same chip. Different frequencies could be used for logic operations and control of other nearby qubits, for instance. Smaller traps could enable faster operations if unwanted heating can be suppressed, according to the paper.

Explore further: Controlling light on a chip at the single-photon level

More information: C. Ospelkaus, U. Warring, Y. Colombe, K.R. Brown, J.M. Amini, D. Leibfried and D.J. Wineland. 2011. Microwave quantum logic gates for trapped ions. Nature. August 11.

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holoman
1 / 5 (1) Aug 10, 2011
This Nanotechnology already has 2 patents ?

http://colossalstorage.net
Telekinetic
2.8 / 5 (4) Aug 10, 2011
Entanglement is the most mind-boggling phenomenon of all. Is our universe really just a hologram? How else, or by what other means, channel, conduit or medium do two particles instantaneously, with zero lag time, mirror the other's behavior?
technodiss
5 / 5 (2) Aug 10, 2011
Entanglement is the most mind-boggling phenomenon of all. Is our universe really just a hologram? How else, or by what other means, channel, conduit or medium do two particles instantaneously, with zero lag time, mirror the other's behavior?

as we delve deeper into the quantum universe, we may find that these interactions are not instantaneous. it may take a vastly superior quantum computer to fully (or even come close to) understand(ing) the phenomena of entanglement. maybe proving extra dimensions or string theory or other, even stranger, future theories only hinted at with today's understandings.
brant
3.7 / 5 (3) Aug 10, 2011
Entanglement is the most mind-boggling phenomenon of all. Is our universe really just a hologram? How else, or by what other means, channel, conduit or medium do two particles instantaneously, with zero lag time, mirror the other's behavior?


If you think about the fact that all particles come from the same faster than light energy substrate, they are all connected intimately. We cant see the connection normally because our instrumentation is not capable.
We have just started learning how to manipulate the aether(entanglement).
Techno1
2.1 / 5 (7) Aug 10, 2011
How else, or by what other means, channel, conduit or medium do two particles instantaneously, with zero lag time, mirror the other's behavior?


Lot's of plausible hypothesis on this one:

Extra dimensions
Complex dimensions
exotic forces previously undescribed
Exotic geometries

Have you ever played Final Fantasy 6?

"The World is Square".

remember? You go off the right side of the screen and come back on the left. You go off the top and come back on the bottom.

There is no "real world" geometrical interpretation of this, even though it corresponds slightly to a torus, it does not represent circular or toroidal geometry. The airship "teleports" from one side of the map to the other.

Even though this makes no sense in the real world, in the game engine, there is a perfectly logical, mathematical algorithm which causes this, and by design.

Point is, order exists, even if it is "nonsense" from our perspective.

or, my favorite:

Misinterpretation
Techno1
3 / 5 (4) Aug 10, 2011
So the point I'm getting at is the mathematics of the underlying reality may be more complicated than a casual, naive observation implies.

Just because two particles are at a distance in 3 dimensions doesn't prove they are at a distance in the 4th dimension. If you imagine space as being "folded" through a 4th dimension, then it's possible for the two "entangled" particles to be in physical contact in the 4th dimension, while still being seperated in the 3 dimensions we are familliar with.

Similarly, if you have a piece of paper in 2d, the ends are seperated in the 2d dimensions, events here are at a distance. However, if you roll it up in the 3rd dimension, then your "ends" become co-located, and events are no longer seperated in space.

Therefore, a geometrical interpretation of entanglement between distance particles is that "space-time" between the particles is folded into another dimension, "invisible", along which the particles are in physical contact.
Techno1
1.8 / 5 (5) Aug 10, 2011
Therefore, changing the state of distant objects via entanglement in quantum experiments represents physical contact, or some other forcing between particles where the force vectors are being applied in and along the 5th dimension, or some other dimension, with space and time being the first 4 dimensions.

That is, entangled objects sit at opposite ends of an infinitesmally narrow wormhole which is oriented in the 5th dimenion and connects two locations in ordinary space-time.

Think of this as a "straw" passing through an apple, taking a "shortcut" from one side to the other, as an analogy, albeit imperfect analogy.

Since the wormhole has an infinitesmal width, probably planck number, there is only exactly one entrance and exactly one exit.

It either does not exist in ordinary dimensions, or it is so small it cannot be directly observed, but the EFFECTS can be observed, and we mistakenly refer to this effect as "Entanglement"...
Techno1
1.8 / 5 (5) Aug 10, 2011
Because in experiments the objects entangled are relatively close, and usually of very, very tiny mass, the energy required to open the wormhole is itself incredibly tiny.

There have only been a few entanglement experiments over long distances, and very few experiments of macroscopic nature. All of them have happened on the surface of the earth, within a tiny, tiny fraction of a light-second of one another...

So the distance is negligible compared to cosmic scales of dimension, and the mass is usually a photon, or at most an atom or molecule.

From a cosmic scale, entangling atoms on opposite sides of the planet is insignificant fraction of the length of the dimensions of the universe both in space and time.

It is essentially a "temporary" space axis which exists ONLY between the entangled particles, and as such, requires an insignificant amount of energy to produce, because the distance along that axis is near-zero.

Tunneling can be explained by the same interpretation
Techno1
2 / 5 (5) Aug 10, 2011
Rossi's cold fusion may even be explained by a wormhole or tunneling effect.

After all, if the distance between the particles in the 5th dimension is zero, then the Proton could move "through" the wormhole and end up "inside" the nucleus of the Nickel atom, creating fusion without paying any "costs" of overcoming the nuclear forces...

While this seems exceptionally convenient, there's no good reason it couldn't happen via simple linear motion in the 5th dimension, if the 5th dimension exists...
Techno1
1.8 / 5 (5) Aug 10, 2011
That's all BS anyway, 'cause nobody can falsify it, right?

Anyway, at the rate classical computers are improving, there might not be much real-world benefits from quantum computers.

Once classical computers get to the molecular or atomic scale, it probably won't matter much about anything else nobody knows how to solve at the moment.

They'll probably be able to simulate it on a trillion-core classical computer and figure it out anyway...
Callippo
1 / 5 (2) Aug 10, 2011
Entanglement is the most mind-boggling phenomenon of all. Is our universe really just a hologram? How else, or by what other means, channel, conduit or medium do two particles instantaneously, with zero lag time, mirror the other's behavior?
An aether is much easier to understand explanation. In particle environment it's quite normal, energy is shared in both transverse, both longitudinal waves. But the later ones are always a much faster, than the former.

You can imagine it like the interaction of pair of solitons occurring at the water surface. These solitons can indeed communicate via surface waves - but the underwater waves are in play, too.
Callippo
1 / 5 (1) Aug 10, 2011
Rossi's cold fusion may even be explained by a wormhole or tunneling effect.
IMO it could be explained in a much more convenient way too. At the case of fusion of pair hydrogen atoms the electrons (which are surrounding them) pose no shielding from repulsive Coulombic force of protons (i.e. hydrogen atom nuclei). But when atom nuclei are surrounded with hole crowd of electrons (like at the case of nickel nuclei), then the electrons form an effective shield of Coulombic barrier, just because there is many of them. You cannot push one electron from nuclei so easily in such a situation - the other electrons are moving collectively and they must but pushed too like single body. In such case, the nickel nuclei is surrounded with rigid crust of many electrons, which are itself attractive to protons and they're shielding their Coulomb barrier effectively.
Callippo
1 / 5 (2) Aug 10, 2011
Anyway, at the rate classical computers are improving, there might not be much real-world benefits from quantum computers.
You're absolutely right, both types of computer converge to the same target of information speed/density, limited just with uncertainty principle. It means, at the room temperature the stability of quantum computers would require such a quabit redundancy, their computational power will become equivalent to the classical computers. I don't see a huge advantage here from perspective of common consumer electronics.
Techno1
2 / 5 (4) Aug 11, 2011
You're absolutely right, both types of computer converge to the same target of information speed/density, limited just with uncertainty principle.


Well, no, I wouldn't say that.

The quantum computer can verifiably, at least in theory, solve certain classes of problems in fewer steps.

The issue is whether there's any real-world benefit to that in ordinary circumstances.

Already, signal delay between servers in different locations in the world is becoming a significant fraction of the total processing time it takes between distant computers.

Even if you had magical computers that solved everything in one operation, you'd still have a 0.1335 second signal propagation to circum-navigate the earth on the shortes possible round-trip around the equator...

Let's say if it takes you 5 seconds to load this web page, then even with fairy tale computers you still couldn't get below 0.1335 seconds, which is only an improvement of a factor of 37.5.
Techno1
1 / 5 (3) Aug 11, 2011
Now let's say you have a quantum algorithm dealing with some data set, and N is the operations a classic algorithm would be, and sqrt(N) is the quantum. and N is a million, then quantum is 1000 operations.

Doesn't even matter in human terms. My computer has 4 processor cores, and each does 2.88 BILLION clock cycles per second.

My human brain would not even notice the difference between the quantum calculaton and the classical calculation, even when N equals a million, because the brain works with millisecond signal propagation delays...

that doesn't make it totally worthless, but seeing as how humans are usually the ones doing input, there's not much room for improvement, since we only do the same old shit with this stuff anyway.

Admittedly, on the SERVER SIDE, the quantum computer would make a huge difference, but on client side it barely even matters, because the useer is usually sitting there reading or doing something else, continued...
Techno1
2 / 5 (4) Aug 11, 2011
So then while I'm reading or typing, the CPU, video card, and monitor are refreshing the screen several dozen times per second, waiting on my primitive brain to work a few characters per second.

The CPU alone could be doing 11 billion clock cycles per second, not counting the several-hundred-stream- processors video card, and sound card, but it doesn't really have any instructions unless I hit a key stroke or click a link. It turns out the computer is only doing a handfull of relevant calculations per second in browsing and posting on a forum...

Now if you find a class of problems that a quantum computer can solve through quantum tricks, but that a classical computer cannot solve, then that would be beneficial. however, most of such problesm would only be useful in astrophysics, theoretical physics, meteorology, or in modelling protein folding, nano-machines, or brain chemistry. Normal people will have no use whatsoever for this sort of calculation on a daily basis.
Techno1
1.8 / 5 (5) Aug 11, 2011
Meteorology might not even benefit from quantum computers.

They'd need to improve the resolution of observations and data inputs in both space and time by like 10 or 11 orders of magnitude before quantum calculations would become beneficial for global computer models...The computers are already able to model the weather to a higher resolution than they have instrumentation for input data, so improving the computers will hardly even matter, until they get more types of measurements, more accurate measurements, taken at more weather stations, radars, and buoys, and taken more often in time.

If you quadruple the resolution of measurements in space, and double the resolution in time, and have a computer 8 times more powerful to run it on, it would require 4 times as many weather stations, buoys, radars, weather satellites, etc, and would only provide a marginal, possibly even un-noticeable, improvement to the accuracy and precision of forecasts of severe weather and hurricanes...
alchemistdagger
not rated yet Aug 11, 2011
would it be theoretically possible based on this article to have two entangled particles and send one on a satellite or spaceship with the other one here on earth and allow faster than light communication? for example with the mars rovers or a satellite sent to jupiter?
rawa1
1 / 5 (2) Aug 11, 2011
would it be theoretically possible based on this article to have two entangled particles and send one on a satellite or spaceship with the other one here on earth and allow faster than light communication? for example with the mars rovers or a satellite sent to jupiter?
IMO not because of decoherence. But the limit given with quantum fluctuations of vacuum could be extended with using of multiple detectors, increasing of signal strength and/or repetition of communication on background of principle of so-called weak measurement.

Such arrangement would allow us to break light speed limit into account of locality and determinism of such communication (you can be never sure with your partner in discussion and/or time, when the signal transmission succeeds). It's normal aspect of longitudinal wave spreading in air too.
rawa1
1 / 5 (1) Aug 11, 2011
As an extreme case of superluminal observation could serve the explosion of supernova inside of nearby galaxy, which would behave like explosion of nuclear bomb beneath the water surface. A well before the surface ripples could reach the observer of the water surface, we would experience the shock wave of sound from underwater, which would manifest like less or more sudden change of intensity of Brownian noise at the water surface. You can observe this phenomena on the YT video of nuclear test Hardtack bellow.

http://www.youtub...zMGjXDUc

At the case of supernova we would observe the sudden change of CMBR noise intensity and this change would propagate at least 10E 10 faster than the light through our Universe. Such change would appear from all directions at the same moment, so it wouldn't violate the relativistic speed limit for deterministic communication/observation. Such events were already detected at GEO-600 observatory and interpreted like the "holographic noise"
c0y0te
not rated yet Aug 11, 2011
Now if you find a class of problems that a quantum computer can solve through quantum tricks, but that a classical computer cannot solve, then that would be beneficial. however, most of such problesm would only be useful in astrophysics, theoretical physics, meteorology, or in modelling protein folding, nano-machines, or brain chemistry. Normal people will have no use whatsoever for this sort of calculation on a daily basis.


You reminded me of a colleague of mine from work. I was sitting programming, and he (a TV repair guy) came to me and said that he really didn't understand what computers really were for because couple of decades ago everything had been done quite OK without them.

I'm sure that as nowadays computers came into every part of our life that quantum computers one day will too. Even if they don't, if that protein folding or nano-machines lead to a cancer cure, a large part of "normal" people will indirectly benefit from those calculations on a daily basis.
Techno1
1 / 5 (2) Aug 11, 2011
Even if they don't, if that protein folding or nano-machines lead to a cancer cure, a large part of "normal" people will indirectly benefit from those calculations on a daily basis.


Of course that would benefit people. That's why I mentioned it.

But you've got to realize most people don't even understand the technology we are using now, not even at the conceptual level, nevermind technical details and programming.

Some of the newest smartphones are already dual core, and like I said, the vast majority of people do nothing but play games or make a telephone call with them.

They don't even do stuff like what I thought of on the SETI article, nobody does, but there's no good reason such a network couldn't be made, with the funds available.

In about 5 years, photonic processors will be available, and regardless of photonics, the electronic computers will be using 6nm transistors, and they'll be in smart phones, and all people will do with them is make phone calls..
Techno1
1 / 5 (2) Aug 11, 2011
And you miss my point.

I have not a failure of imagination, trust me, I know many uses for this technology and computatonal power: Self-Assembling, Self-Replicating, Self-Repairing Robotics.

Entertainment will always find a way to hog processor time with more and more color depth beyond human perception, more frames per second beyond human perception, 3d modeling, and yes, even holograms like in Star Trek, to the limits of the laws of physics.

However, improvements in entertainment really just fall on the category of "Doing the same old thing" with it. There have always been improvements in entertainment, and to be honest, the "improvements" aren't even improvements.

It took Blizzard Entertainment THIRTEEN YEARS, (ok ten years of actual coding, modeling, and tweaking,) to make the sequel to one of their games, and when you turn down the excessive shading and color depth which your brain cannot even percieve anyway, it runs well on a 4 core, 2.88ghz processor.
Techno1
2 / 5 (4) Aug 11, 2011
Now blizzard is a bit more obsessive about perfection and appealing to the elite gamers than most companies, so they spent a lot more time than most, but the point is, it now takes 5 to 10 YEARS to make a video game that legitimately needs the processing power of a computer you can buy at Office Depot in the BARGAIN BIN.

You can now get a 6 core processor at 3.2ghz for $179, which is an 11% improvement in clock speed and a 50% improvement in core count, and this is "only" using a 45nm transistor process, because this technology is actually already about 3 years old.

This does not use several improvements in logic gate technology which were invented in the past year or so, which would instantly make it about 15% faster clock speed, not to mention minaturization itself always seems to make things faster and use less energy...

So they might make a video game one day to humble a 100 core, 10ghz processor, but it would take decades for the programmers to make the thing...
Techno1
1 / 5 (1) Aug 11, 2011
They would need to invent A.I. or an "Expert Machine" specifically for helping convert concept art to 3d models, because it takes humans too long to do it, and the higher the color depth, and the more frames and unique directions you want for the model, the more complicated and difficult it becomes. Double the color depth and you double the detail. Double the pixels and you double the detail again.

Double the size of the game engine, and the number of unique enteractions of characters, and you double the difficulty of making the game again...

Well, let's see, I made just 3 doublings, so that would be 8 times more complicated.

So that would take Blizzard 80 years to make using the same technologies and HUMAN processes they used on Starcraft 2.

Humans are manually doing 99.9% of the design and making of stuff, because it is, after all, the human's ideas.

So unless you have an A.I. making games for humans, there's no way companies are going make games of this complexity.
antialias_physorg
1 / 5 (1) Aug 11, 2011
Anyway, at the rate classical computers are improving, there might not be much real-world benefits from quantum computers.

Not realy since quantum computers are exceedingly efficient at some types calculations which conventional architecture can't handle efficiently (even if we extrapolate Moore's law for a long time to come). Large prime number factorization (cryptography), parsing, large list sorting, ...

On the other hand quantum computing is pretty bad at some other types of calculations which conventional computers excel at (e.g. basic math operations).

The two types have different applications, and we'll likely see a hybrid architecture rather than one making the other obsolete (i.e. we'll probably have computers which has n conventional and m quantum 'cores').
Shamus
not rated yet Aug 11, 2011
Techno, kinda long-winded - i forgot what point you were making by the time I hit the end..
Macksb
1 / 5 (1) Aug 11, 2011
Let me inject a note of heresy. Consider the mechanism by which these ions were entangled--microwaves. And consider the other method--lasers. Both tools operate through oscillations--coherent, precise oscillations and certain specific frequencies.

Now compare that with the mechanisms that create superconductivity, which comes to mind because it also involves pairing (of electrons, in Cooper pairs). BCS theory says lattice vibrations are the mechanism. Lattice vibrations are a type of oscillation. The mechanisms for cuprates and pnictides remain unclear, but oscillations seem to be involved in both cases (orbits or spins, or both--both being types of oscillations).

So my heretical thesis is this: synchronized or coherent oscilations create all types of superconductivity, just as they create quantum entanglement. My reference is Art Winfree's theory of coupled oscillators, circa 1965, which I have applied in other Physorg posts.

Skeptics may fire when ready.

TheGhostofOtto1923
1 / 5 (2) Aug 11, 2011
I have not a failure of imagination, trust me, I know many uses for this technology and computatonal power: Self-Assembling, Self-Replicating, Self-Repairing Robotics.
I think Quantum Conundrum has a failure of his chemical balances. I understand lithium works wonders?
Techno1
1 / 5 (1) Aug 12, 2011
The two types have different applications, and we'll likely see a hybrid architecture rather than one making the other obsolete (i.e. we'll probably have computers which has n conventional and m quantum 'cores'


I realize that, it's pretty obvious.

In fact, existing computers are already a system of many different types of processors, not just the multi-cored cpu everyone thinks about.

Hopefully, we'll have some quantum chips integrated right into the CPU adjacent to each classical processor core, and queried whenever needed.

And see the diamond article where I talked about this, I know about the sqrt(N) returns in QC computing.

http://www.physor...ory.html

It's pretty clear I'm familliar with the concept.

I'm just saying don't expect QC to magically solve all problems.
rynox
not rated yet Aug 15, 2011
would it be theoretically possible based on this article to have two entangled particles and send one on a satellite or spaceship with the other one here on earth and allow faster than light communication? for example with the mars rovers or a satellite sent to jupiter?


Yes. We are 3-d beings with 3-d brains and 3-d instruments in a universe that may possibly have many more dimensions. Peeking into the affects of quantum mechanics seems strange to us, but only because we don't comprehend the universe fully.

...in my opinion.
antialias_physorg
1 / 5 (1) Aug 16, 2011
would it be theoretically possible based on this article to have two entangled particles and send one on a satellite or spaceship with the other one here on earth and allow faster than light communication?

No. The point being: Even though the two may seem linked you cannot know the state until you measure it. So while there seems to be a faster than light 'snapping into a state' at the other end upon measurement of one end you don't know what you'll measure. So you cannot manipulate the information you want to send.

Information transmission has TWO prerequisites:
1) Convey something from A to B
2) Modulate that something at A in a KNOWN way (i.e. imprint information on it)

For entanglement the second prerequisite does not hold. You cannot *force* the particle at A to behave in a way that would *force* the particle at B to behave in the same way without breaking the entanglement.
TheGhostofOtto1923
1 / 5 (2) Aug 16, 2011
I had thought that you could send a stream of entangled particles out in a cadence while storing their partners. Modifying the stored partners would interrupt the cadence in decipherable ways, which would similarly change the particles in the stream, and this could be used to communicate.

But I am told no, this would not work but I still dont understand why. Care to take a shot?
antialias_physorg
1 / 5 (1) Aug 16, 2011
I had thought that you could send a stream of entangled particles out in a cadence while storing their partners. Modifying the stored partners would interrupt the cadence in decipherable ways,

Nope - because you cannot tell if a particle is entangled or not. So measuring some at point A won't give you any different/observable/measurable alteration at point B.

Measurement does not alter the state (it only fixes it). To transmit information this way you would have to be able to *alter* a state at point A which then flips the particle into the same state at point B.

But entanglement just says whatever you *measure* at point A will be the same with the entangled particle at point B.

Flipping e.g. the spin of the particle at point A afterwards will have no effect on the particle at point B.
TheGhostofOtto1923
1 / 5 (2) Aug 17, 2011
you cannot tell if a particle is entangled or not.
But the receiver knows he is measuring a stream of entangled particles -?
But entanglement just says whatever you *measure* at point A will be the same with the entangled particle at point B.
Correct. So if the receiver measures a stream of particles with the same spin value, and then receives one with a different value, he will know the sender has changed its stored partner; info has been transmitted.
Flipping e.g. the spin of the particle at point A afterwards will have no effect on the particle at point B.
"When a measurement is made and it causes one member of such a pair to take on a definite value (e.g., clockwise spin), the other member of this entangled pair WILL at any subsequent time BE FOUND to have taken the complementary value (e.g., counterclockwise spin). Thus, there is a correlation between the results of measurements performed on entangled pairs, and this occurs even though [separated]"
antialias_physorg
1 / 5 (1) Aug 17, 2011
"When a measurement is made and it causes one member of such a pair to take on a definite value (e.g., clockwise spin), the other member of this entangled pair WILL at any subsequent time BE FOUND to have taken the complementary value (e.g., counterclockwise spin). Thus, there is a correlation between the results of measurements performed on entangled pairs, and this occurs even though [separated]"

No. What you do to one particle _after_ it is entangled does not get transmitted (if you do anything to it you just break the entanglement). Forcibly flipping the spin of one after the two are separated has no impact on the spin of the other.

Only the entangled state (i.e. the state that the particles are in at the point/time of entanglement) will cause the particles to exhibit identical properties upon measurement.

But in that case you're simply transmitting particles with known state (which is not FTL because the transmission of the particle itself will be at less than c)
TheGhostofOtto1923
1 / 5 (2) Aug 17, 2011
No. What you do to one particle _after_ it is entangled does not get transmitted (if you do anything to it you just break the entanglement).
SURE it does. Read this again:

"When a measurement is made and it causes one member of such a pair to take on a definite value (e.g., clockwise spin), the other member of this entangled pair WILL at any subsequent time BE FOUND to have taken the complementary value (e.g., counterclockwise spin)."

-However,

"If each of two hypothetical experimenters, Alice and Bob, has one of the particles that form an entangled pair, and Alice measures the spin of her particle, the measurement will be entirely UNPREDICTABLE, with a 50% probability of the spin being up or down. And if Bob subsequently measures the spin of his particle, the measurement will be entirely PREDICTABLE..."

-And this predictability is the info that cannot be transmitted from the transmitter to the receiver FTL.
cont
TheGhostofOtto1923
1 / 5 (2) Aug 17, 2011
The question is, can entangled pairs be created where the state is entirely known without having to measure them? Can a stream of particles be created so that if one is altered this can be discerned by the receiver as he is measuring each particle?

"it is impossible to prepare a simultaneous eigenstate for all observables. For example, we cannot prepare a state such that both the position measurement Q(t) and the momentum measurement P(t) (at the same time t) produce "sharp" results; at least one of them will exhibit random behaviour. This is the content of the Heisenberg uncertainty relation."

-Maybe so maybe so.

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