Entangled Particles Break Classical Law of Thermodynamics, Say Physicists

Entangled Particles Break Classical Law of Thermodynamics, Say Physicists:  A couple of years ago, we looked at an experimental version of Maxwell's demon, in which Japanese physicists created a kind of staircase in which they lowered an energy barrier to allow atoms to jump up a step and then raised it to prevent the atom falling back down again...

However, what was extraordinary about the Japanese experiment is that it converted information into energy...



Imagine two boxes of particles with trap door between them. You want to use the trap door to guide the faster particles into one box and the slower particles into the other. In a classical experiment you would have to measure the particles in both boxes to do this experiment.

But things are different if the particles in one box are entangled with the particles in the other. In that case, measurements on the particles in one box give you info about both sets of particles.

In essence, you're getting information for nothing. And since you can convert that information into energy, there is clear advantage when entanglement plays a role.

That's hugely significant. It means that the laws of thermodynamics depend not only on classical phenomenon and information but on quantum effects  too. The breakthrough that Funo and co make is to extend the theory to take this into account. "We show that entangled states can be used to extract thermodynamic work beyond classical correlation," they say.

How Maxwell's Demon Cools a Gas to Microkelvin Temperatures [Animation]: Scientific American

How Maxwell's Demon Cools a Gas to Microkelvin Temperatures [Animation]: Scientific American: Raizen's idea is that a one-way gate can help cool a gas in two steps: First let the gate concentrate atoms into a smaller volume (but without raising their temperature), then allow them to expand to the original volume (which brings their temperature down).

Click on "START" to see how it works.

Demons, Entropy, and the Quest for Absolute Zero: Scientific American

Demons, Entropy, and the Quest for Absolute Zero: Scientific American: For the one-way gate to work, I reasoned, the atoms in the gas must have two different states (possible configurations of orbiting electrons) that are both of low energy and thus stable. Let us call the two states blue and red. The atoms are suspended in a container that is cut across the middle by a laser beam. The beam is tuned to a wavelength that makes red atoms bounce back when they approach it, so that it acts in essence as a closed gate. Initially all atoms are blue and thus can fly through the laser barrier unimpeded. But just to the right of the barrier beam, atoms are hit by a second laser, this one tuned so that atoms turn from blue to red by scattering a single photon. Now the atoms, being red, are repelled by the barrier beam and thus cannot go through the gate and back to the left side. Eventually all the atoms gather up on the right side, and the left side remains empty.

Scientists show how to erase information without using energy

Scientists show how to erase information without using energy: "However, Vaccaro and Barnett have shown that an energy cost can be fully avoided by using a reservoir based on something other than energy, such as spin angular momentum. Subatomic particles have spin angular momentum, a quantity that, like energy, must be conserved. Basically, instead of heat being exchanged between a qubit and thermal reservoir, discrete quanta of angular momentum are exchanged between a qubit and spin reservoir. The scientists described how repeated logic operations between the qubit’s spin and a secondary spin in the zero state eventually result in both spins reaching the logical zero state. Most importantly, the scientists showed that the cost of erasing the qubit’s memory is given in terms of the quantity defining the logic states, which in this case is spin angular momentum and not energy."

Summon a 'demon' to turn information into energy - physics-math - 15 November 2010 - New Scientist

Summon a 'demon' to turn information into energy: The rotor is formed from two linked polystyrene beads each 0.3 micrometres across. One is pinned to a glass surface leaving the other free to rotate around it and the whole thing is immersed in fluid. Buffeted by molecules of the fluid, the rotor turns clockwise as often as it does anti-clockwise.

But then the researchers add a complex electric field that applies a gentle torque to the rotor, which varies at different angles. The torque is analogous to the force of gravity acting on the tiny ball on a staircase...

Finally, enter the demon, whose eye is a camera and brain a computer that controls the electric field. Whenever the rotor makes some progress in turning against the torque, the demon shifts the electric field so that the rotor suddenly finds itself nudged onto the top of that "step". This keeps happening, and the overall effect is to gradually climb the staircase.

Technology Review: Blogs: arXiv blog: Physicists Convert Information Into Energy

Technology Review: Blogs: arXiv blog: Physicists Convert Information Into Energy: "Toyabe and co's work is an experimental version of the famous Maxwell's demon...

But here's the curious thing. There is no conventional transfer of energy into the system: no heating or accelerating of molecules or some such. Instead, information itself seems to be the medium through which energy is transferred...

It's hard to overstate the significance of what they've done: they've been able to operate a nanomachine--a stair-climbing bead--using nothing more than information as the power supply..."