Hi There, I've been spending some of my free time learning about Quantum Mechanics. This was all going somewhat smoothly, until I encountered something known as "Entanglement Swapping" while learning about loophole free bell tests, such as the one conducted by Hensen et al at TU Delft in 2015. While I'm no professional physicist and thus it is highly likely that I'm misunderstanding something. It appears that entanglement swapping can be exploited to determine the absolute velocity of object, in defiance of the first postulate of special relativity. To explain why this appears to be the case, I've devised a thought experiment called the Spooky Speedometer. Experiment Configuration On board a spacecraft, Alice and Bob float into a room dressed in space suits and evacuate all the air out of the room.Alice takes her place on left side of the room, while Bob takes his place on the right. Alice places two tiny diamonds, each containing a nitrogen vacancy, side by side. Bob in turn, sets up an entanglement swapping device at the other end of the room. Alice also brought two lasers into the room, which she can use to excite a trapped electron within each of the diamonds, causing each to emit a photon that is entangled with its emitting electron. Once the photons are emitted, Alice can choose at any moment to measure the spin of both her electrons. Alice's diamonds are configured so that emitted photons will traverse the vacuum of the room and enter Bob's entanglement swapping device simultaneously. This will result in the electrons, which were not initially entangled with each other, becoming instantaneously entangled. Performing the Experiment Initially, Alice uses her lasers to cause her electrons to emit entangled photons and then immediately measures her electrons. She repeats this process a number of times, in order to determine with a high degree of certainty, if her electrons are entangled. However, as insufficient time has passed for the photons to reach Bob's entanglement swapping device, they will not be entangled. Alice subsequently increases the time elapsed between emitting and measuring, in very small increments, performing multiple measurements at each increment, until an elapsed time is reached which produces entangled electrons. This elapsed time is the same time taken for the photons to traverse from Alice to Bob. Analysing the result If the spacecraft is stationary, the time required for the photons to traverse the room, can be calculated by the below formula: tAlice = d/c where: tAlice: The time it takes for the photons to traverse the room according to Alice's experiment d: The distance between Alice and Bob when the spacecraft is at rest. c: The speed of light in a vacuum However, if the spacecraft has motion along the axis of the photon pathway, the formula is a little more complex for the observer at rest. For instance, the stationary observer will measure the distance between Alice and Bob as reduced due to Lorentz contraction: d/γ Where: γ: The Lorentz factor Similarly, Alice's measurement of time is slowed by Lorentz dilation: trest = γtAlice Where: trest: The time it takes for the photons to traverse the room according to a stationary observer Additionally, for an observer at rest, the relative speed of the photons in relation to the spacecraft, will vary from speed of light, if the spacecraft is in motion: c + v Where: v: The absolute velocity of the spacecraft along the axis of the photon pathway (motion from Bob to Alice considered positive) Thus, for a stationary reference frame, the time taken for the photons to traverse the room is given by the below formula: trest = γtAlice = d/(γ(c + v)) Once Alice has determined the elapsed time via the experiment, she can rearrange the prior formula and determine the absolute velocity of the spacecraft along the axis of photon pathway: v = c - ((tAlicec^2)/d) [see page three of link for each step: https://drive.google.com/open?id=0B3K5GT7ukRAKM05PYVVmSC1XejA ] Alice could have approached measuring the elapsed time in a simpler manner, by asking Bob the time at which the photons reach his entanglement swapping device and deducting from it the time which she emitted them. However, this measurement method would be impacted by time dilation, length contraction, aberration of light and relativity of simultaneity, so that when inputted into the above formula, it would always output the spacecraft as being stationary. By utilising entanglement swapping (as I understand it to work), the spooky speedometer experiment can determine the absolute velocity of an object (the spacecraft in this thought experiment), along the axis of the photon pathway. Thus, this leads me to conclude that either: 1. My understanding of entanglement swapping is flawed or, 2. Special Relativity is flawed. Obviously the later would be highly improbable. So, I'm expecting that one of you will be able to articulate why it is the former. Any assistance getting to the bottom of this is much appreciated. If you want me to elaborate, please feel free to ask.