3,000 entangled atoms tame the ticks of atomic clocksMd Noman Siddique (Author) Published Date : Mar 31, 2015 10:19 IST
University of Belgrade boffins and MIT have taken a giant leap in applying quantum property entanglement to macro systems and are claiming to have roped together over 2,900 rubidium atoms using a single photon.
Lead author Vladan Vuletic calls this a new class of entangled states in the work that they expect will help in the creation of atomic clocks that are even more precise (because clocks that drift less than one second over the life of the Sun is still inaccurate).
A canned release from MIT explains that one way of improving accuracy of clock is by entangling lots of atoms.
A classical-physics atomic clock bases oscillation of atoms in a cloud and is proportional to the square root of the number of atoms (nine times as many atoms provide a clock three times as accurate).
MIT adds that by applying entanglement to the cloud, it is possible to turn the square root relationship to a linear relationship and for instance, when accuracy is to be tripled, it needs only 3 times atoms. In the world of atomic time keeping, entangling 3,000 atoms is therefore a big deal.
Mutual entanglement was achieved by initially cooling the atoms close to zero and held in that state with the help of a laser trap. Researchers then dispatched a weak laser pulse through the cloud after setting up a detector to trace a particular photon in the beam.
As Physicsworld explains:
The experiment involves an optical cavity two opposing imperfect mirrors containing about 3100 rubidium-87 atoms that are cooled to a temperature of near absolute zero. Light is shone into one side of the cavity and allowed to bounce back and forth between the mirrors. Some of the light will eventually escape through the opposite side of the cavity, where it is captured by a detector. A magnetic field is applied to the atoms, which causes them to align their spins along the length of the cavity. However, the probabilistic nature of quantum mechanics means that the spins are not all aligned and their directions will fluctuate about the magnetic field.
MIT's release explains Vuleti 's reasoning thus: if a photon has passed through the atom cloud without event, its polarization would remain the same. If, however, a photon has interacted with the atoms, its polarization rotates just slightly .
Quantum noise affecting the atom s ensemble is indicated by the change to polarization of the photon.
The lead author also adds that when the polarization of an exiting proton is perpendicular to its polarization on its entry, we know the possible cause to be the atomic ensemble ... that detection generates a very strongly entangled state of the atoms
According to MIT previously the largest number of mutual entanglement was 100 atoms, although its press release is silent on the authors of the previous work. The paper presented by Vuletic however refers to an entanglement between 100 photons in 2013 which is possibly what the press office meant, going by the general quality of science communications.
3,000 entangled atoms tame the ticks of atomic clocks