NASA Emdrive tests consistently measured performance at 1.2 ± 0.1 mN∕kW, which was very close to the average impulsive performance measured in air. A number of error sources were considered and discussed.
Emdrive is 300 times better than light sails, laser propulsion and photon rockets on thrust to power level basis
Missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements. The 1.2 mN∕kW performance parameter is over two orders of magnitude higher than other forms of ‘zero propellant’ propulsion, such as light sails, laser propulsion, and photon rockets having thrust-to-power levels in the 3.33–6.67 μN∕kW (or 0.0033–0.0067 mN∕kW) range.
A physics model used to derive a force was a nonlocal hidden-variable theory aka pilot-wave theory.
An experiment claims to have invalidated a decades-old criticism against pilot-wave theory, an alternative formulation of quantum mechanics that avoids the most baffling features of the subatomic universe.
The differences between Bohm and Copenhagen become clear when we look at the classic “double slit” experiment, in which particles (let’s say electrons) pass through a pair of narrow slits, eventually reaching a screen where each particle can be recorded. When the experiment is carried out, the electrons behave like waves, creating on the screen a particular pattern called an “interference pattern.” Remarkably, this pattern gradually emerges even if the electrons are sent one at a time, suggesting that each electron passes through both slits simultaneously.
Those who embrace the Copenhagen view have come to live with this state of affairs — after all, it’s meaningless to speak of a particle’s position until we measure it. Some physicists are drawn instead to the Many Worlds interpretation of quantum mechanics, in which observers in some universes see the electron go through the left slit, while those in other universes see it go through the right slit — which is fine, if you’re comfortable with an infinite array of unseen universes.
By comparison, the Bohmian view sounds rather tame: The electrons act like actual particles, their velocities at any moment fully determined by the pilot wave, which in turn depends on the wave function. In this view, each electron is like a surfer: It occupies a particular place at every specific moment in time, yet its motion is dictated by the motion of a spread-out wave. Although each electron takes a fully determined path through just one slit, the pilot wave passes through both slits. The end result exactly matches the pattern one sees in standard quantum mechanics.
For some theorists, the Bohmian interpretation holds an irresistible appeal. “All you have to do to make sense of quantum mechanics is to say to yourself: When we talk about particles, we really mean particles. Then all the problems go away,” said Goldstein. “Things have positions. They are somewhere. If you take that idea seriously, you’re led almost immediately to Bohm. It’s a far simpler version of quantum mechanics than what you find in the textbooks.”
The farther the first photon travels, the less reliable the second photon’s report becomes. The reason is nonlocality. Because the two photons are entangled, the path that the first photon takes will affect the polarization of the second photon. By the time the first photon reaches the screen, the second photon’s polarization is equally likely to be oriented one way as the other — thus giving it “no opinion,” so to speak, as to whether the first photon took the first route or the second (the equivalent of knowing which of the two slits it went through).
The problem isn’t that Bohm trajectories are surreal, said Steinberg. The problem is that the second photon says that Bohm trajectories are surreal — and, thanks to nonlocality, its report is not to be trusted. “There’s no real contradiction in there,” said Steinberg. “You just have to always bear in mind the nonlocality, or you miss something very important.”
Science Advances - Experimental nonlocal and surreal Bohmian trajectories
Weak measurement allows one to empirically determine a set of average trajectories for an ensemble of quantum particles. However, when two particles are entangled, the trajectories of the first particle can depend nonlocally on the position of the second particle. Moreover, the theory describing these trajectories, called Bohmian mechanics, predicts trajectories that were at first deemed “surreal” when the second particle is used to probe the position of the first particle. We entangle two photons and determine a set of Bohmian trajectories for one of them using weak measurements and postselection. We show that the trajectories seem surreal only if one ignores their manifest nonlocality.
SOURCES- Wired, Science Advances, Journal of Propulsion and Power