At 4:33 PM 9/17/4, Keith Nagel wrote: >Hi Horace, > >You'd be surprised at some of the lurkers here. Wish they'd >put a nickel in the slot every once and a while. > >I'm a little confused about why this is such an accomplishment.
I do not have enough information or understanding of the actual experiment to comment. I know only what was posted. However, I will still have the audacity to comment from the basis of general principles involved in the issue, yet which I do not fully understand either! I expect the act of engaging the subject may lead to a better probability of my understanding some apsects of it! 8^) >Let me describe an experimental setup I worked with for >some time, that has relevance to this. > >The experiment was designed to measure wave speed, and we >needed a way to synchronize two detectors at a distance >from one another. The solution was very simple. The >detectors are equidistant, at the center was a pulse >generator. A pair of air core transmission lines lead >one to each detector. A pulse from the generator would >arrive simultaneously at each detector, giving a light >speed delayed timed pulse to each. Because the detectors >were equidistant, they could be matched to within >the resolution of the pulse rising edge ( ~ 10 ps ). >The limit was the edge detection, it could have been >1 ps if that was needed. I think the above is a false assumption. Temperatures are not the same everywhere, and tempertures are typically in a state of change. The problem of clock synchonization, it seems to me, boils down to knowing were you are in *both* space and time, at a given moment. The length of one cable can changed by simply being heated up or cooled down. Even if light beams are used, the distance between two places on the surface of the earth can change just by heating of the earth's crust, or by seismic activity. Light moves at 3x10^8 m/s, so a nanosecond is about 30 cm, and a picosecond is a mere 0.3 mm. Knowing the time delay of a light speed signal to the nearest nanosecond in an approximately 2 km test requires knowing the distance doesn't change by more than .3/2000 = =1.5x10-4, or 0.015 percent. You can see that knowledge of distance plays a very significant role if accuracy down to the picosecond is to be obtained. > >Is this circuit really any different that what's been >described in the AIP bulletin? Again, I don't really know what the circuit is in the AIP described experiment, but will respond based on general considerations of the issue. >What do you think? I have >a hard time getting past "bertlemans socks" despite >reading at some length on the hidden variable problem. Before trying to answer your question, I feel I should first say it strikes me that clock synchronization is not really different from information transfer. If one can even merely (though nearly instantaneously) determine whether two "clocks" are in synchronization, then by frequency modulation of one of the "clocks" one can transfer information. But, that said, let's talk about the value of instantaneous information transfer to clock sunchronization and the hidden variable issues involved here. It seems to me the important thing experimentally is the distance between the clocks (in terms of light path length). The smaller the distance between the clocks, the less the absolute distance can vary during the synchronization, and thus, since light travels at constant speed, the better the synchronization. The experimental variables are more easily controlled the shorter the distance between clocks. Timing precision is limited by the ability to control or to know of any changes in distance during the synchronization. This principle, that increased distance adversely affects synchronization accuracy, goes out the window if instantaneous communication is involved over some large part of the distance between the clocks. The speed of light c then has no relevance to that large portion of the distance. The distance that has relevance to synchronization accuracy is then merely the distance between the quantum entanglement "reciever" and the second clock, including the synchronization circuit, plus similar concerns at the sending end. That said, it seems to me that distance still plays an important role in the instantaneous portion of the communication link, assuming that is, that there is no hidden variable involved in quantum states. If quantum state is not determined until measured, then time of measurment plays an important role. The quantum state is only determined when the state of one of the entangled pair is measured. It can not be known in advance which member of the pair will be the "transmitter" of the quantum state and which will be the "receiver." Whichever member is measured first sets the state that will be measured when the second member is observed. In the discussion that follows, it is assumed that hidden variables do not exist. When an entangled pair is sent to both Alice and Bob, if Alice measures a state first, then Bob is the receiver of the (conjugate) state set when Alice measured it. However, if Bob measures the state of the pair before Alice can set it by measuring, then Alice is (possibly unwittingly) the reciever. Neither can tell which is which, based solely on the receipt of a single photon. However, the FTL communication method I posted is based on measuring the frequencies associated with accumulated results, i.e beam intensity. Since, in the proposed FTL method, the sender Alice's observed frequencies (probabilites) of polarization orientation can be manipulated by choice of path at the sending end, the reciever Bob's observed frequencies will be the same as Alice's (though observed as conjugates) *provided Bob's measurment occurs after Alice initialy observes and thus sets the frequencies/probabilites*. The degree of instantaneousness of the information transfer is dependent upon Alice waiting to the last possible moment to do her measurment, and Bob doing his observation as closly as possible, yet after, the time Alice does her measurment. If the photon pair is sent through the vacuum by an intermediary Charlie located halfway between Alice and Bob, then, to be the reciever, Bob must be located slightly further away from Charlie than Alice. To send, using the same beams, Bob needs to be slightly closer to Charlie than Alice. The precision of such an arrangement with regard to clock synchornization is then limited by control of the incremental distance, not the absolute distance. The signal delay is set by the incremental distance, i.e. the difference between the distance of Alice from Charlie vs Bob from Charlie. Now, you can (I think rightly) say that the variability of the full distance between Alice and Bob is involved in either communication method. However, suppose Bob has an optical bench at his end of the beam, and the center of that bench is located roughly at the mean distance that Alice is from Charlie. The bench is long enough to accomodate the largest change in distance between Bob and Alice, i.e the largest possible time error. Suppose Bob has a sensor that can determine whether the beam has a 50/50 polarization or not, and that this sensor can slide across the bench. When the sensor is at the extreme end of the bench toward Alice, it will receive photons with a 50/50 polarization distribution. That is because Alice has not measured the cojugates yet, and Bob is then the "sender". When Bob's sensor is at the other end of the bench, the signal Alice imposes can be sensed. (It is assumed the device Alice uses to impose the signal is small comapred to the bench size.) Call the point on the bench where the 50-50 signal switches to an information signal the "switch-point". The switch point moves on Bob's bench as the distance between Bob and Alice changes due to extraneous variables. However, if the switch-point moves slowly enough, in comparison to Bob's ability to detect its location, and Bob can quickly switch to a signal reciever further down the bench by known distance x, then the error in knowldge of distance x is all that is involved in the clock synchronization error. Bob only needs the ability to move the switch-point detector and signal detectors in unison fast enough so that the switch-point detector tracks a fixed distance to Alice with the required accuracy. We can now see the difference between the precision of the two methods. The difference between the quantum method vs the deterministic method, is that the precision of the quantum method is based on a small and fairly readily controllable difference of distances vs the overall distance. At least that is what I see from my limited amateur perspective. I could have this all wrong though! Another major difference is that, when using the quantum method, the nature of the signal to be imposed for time synchronization can be changed very close to the time the synchronization is to occur. This would be useful if the synchronization of various clocks needed to occur over, say, interplanitary distances. It is also of interest that the suggested methodology for determining a fixed distance could be used to detect space-warping due to gravity waves, or any other cause. The problem is determining the meaning of space and time. If events can occur instantaneously across any distance, then Einstein's space-time does not adequately describe the universe, and we are left holding a very large bag of unknowns. Regards, Horace Heffner
