In cold-atom chips, atoms are guided above tracks of wires that supply the magnetic field to keep them aloft. In applications ranging from quantum information processing to metrology, any deviation in the magnetic field from point to point over the chip could influence the delicate state of the atoms. Terraciano et al. introduce a technique that takes a snapshot image of the magnetic field landscape. Using a cloud of cold rubidium atoms, whose energy levels are sensitive to magnetic field, they let the cloud fall toward the chip and probe the atoms' state with a laser beam tuned to one of the magnetic transitions. The ability to take a two-dimensional snapshot image of magnetic field variations of 30 mG/cm above the atom chip over 5 mm with 250-μm resolution should prove useful in calibrating these chips for their envisioned applications. — ISOIn cold-atom chips, atoms are guided above tracks of wires that supply the magnetic field to keep them aloft. In applications ranging from quantum information processing to metrology, any deviation in the magnetic field from point to point over the chip could influence the delicate state of the atoms. Terraciano et al. introduce a technique that takes a snapshot image of the magnetic field landscape. Using a cloud of cold rubidium atoms, whose energy levels are sensitive to magnetic field, they let the cloud fall toward the chip and probe the atoms' state with a laser beam tuned to one of the magnetic transitions. The ability to take a two-dimensional snapshot image of magnetic field variations of 30 mG/cm above the atom chip over 5 mm with 250-μm resolution should prove useful in calibrating these chips for their envisioned applications. — ISO

ScienceSep 5, 20080 citations

The Quantum Conundrum

The MIT Press eBooksNov 18, 20250 citations

Physicists take snapshots of quantum measurement

Edwin Cartlidge

Ideal process leaves some superposition states intact, as Edwin Cartlidge reports

Physics WorldApr 1, 20200 citations

Quantum theory of angle and relative-phase measurement

Scott Roger Shepard

The complementarity between time and energy, as well as between an angle and a component of angular momentum, is described at three different layers of understanding. The phenomena of super-resolution are readily apparent in the quantum phase representation which also reveals that entanglement is not required. We modify Schwinger's harmonic oscillator model of angular momentum to include the case of photons. Therein, the quantum angle measurement is shown to be equivalent to the measurement of the relative phase between the two oscillators. Two reasonable ways of dealing with degeneracy are shown to correspond to a conditional measurement which takes a snapshot in absolute time (corresponding to adding probability amplitudes) and a marginal measurement which takes an average in absolute time (corresponding to adding probabilities). The sense in which distinguishability is a ``matter of how long we look'' is discussed and the meaning of the general theory is illustrated by taking the two oscillators to be circularly polarized photons. It is shown that an odd number of $x$ -polarized photons will never have an angle in correspondence with the $y$ axis, but an even number of $x$ -polarized photons always can! The behavior of an $x$ -polarized coherent state is examined and the snapshot angular distributions are seen to evolve into two counter-rotating peaks resulting in considerable correspondence with the $y$ axis at the time for which a classical linear polarization vector would shrink to zero length. We also demonstrate how the probability distribution of absolute time (herein a measurable quantity, rather than just a parameter) has an influence on how these snapshot angular distributions evolve into a quantum version of the polarization ellipse.The complementarity between time and energy, as well as between an angle and a component of angular momentum, is described at three different layers of understanding. The phenomena of super-resolution are readily apparent in the quantum phase representation which also reveals that entanglement is not required. We modify Schwinger's harmonic oscillator model of angular momentum to include the case of photons. Therein, the quantum angle measurement is shown to be equivalent to the measurement of the relative phase between the two oscillators. Two reasonable ways of dealing with degeneracy are shown to correspond to a conditional measurement which takes a snapshot in absolute time (corresponding to adding probability amplitudes) and a marginal measurement which takes an average in absolute time (corresponding to adding probabilities). The sense in which distinguishability is a ``matter of how long we look'' is discussed and the meaning of the general theory is illustrated by taking the two oscillators to be circularly polarized photons. It is shown that an odd number of $x$-polarized photons will never have an angle in correspondence with the $y$ axis, but an even number of $x$-polarized photons always can! The behavior of an $x$-polarized coherent state is examined and the snapshot angular distributions are seen to evolve into two counter-rotating peaks resulting in considerable correspondence with the $y$ axis at the time for which a classical linear polarization vector would shrink to zero length. We also demonstrate how the probability distribution of absolute time (herein a measurable quantity, rather than just a parameter) has an influence on how these snapshot angular distributions evolve into a quantum version of the polarization ellipse.

arXiv:1410.0916Physical Review ADec 12, 20147 citations

Enter the quantum

Princeton University Press eBooksJan 17, 20230 citations

x

-polarized photons will never have an angle in correspondence with the

y

axis, but an even number of

x

-polarized photons always can! The behavior of an

x

-polarized coherent state is examined and the snapshot angular distributions are seen to evolve into two counter-rotating peaks resulting in considerable correspondence with the

y

axis at the time for which a classical linear polarization vector would shrink to zero length. We also demonstrate how the probability distribution of absolute time (herein a measurable quantity, rather than just a parameter) has an influence on how these snapshot angular distributions evolve into a quantum version of the polarization ellipse.