![]() ![]() To settle this dispute, Tonomura and his colleagues made a doughnut-shaped ferromagnet six micrometers in diameter (Fig. If so, the experiment did not prove the existence of the AB effect. there were leakage magnetic fields in space, that could have created the phase differential. As the electron beams contacted the magnet, i.e. Soon after publishing the results, an objection was raised to this experiment. They clearly showed that there is a phase difference between the two electrons beams passing through regions of space that have no magnetic field, and that the extent of the phase difference precisely matches the predicted value. In 1982, using a holography electron microscope Tonomura and his colleagues measured the phase difference in the form of interference fringes produced by two beams of electrons, one passing through the inside and the other passing through the outside of a doughnut-shaped magnet. This enabled him to pick out perfect magnets that do not leak magnetic fields to the outside. This was the basis of a technique known as electron holography, an interference electron microscopy that could be used to show up the contour map of the electron phase. In the 1970s, Tonomura succeeded in making a highly coherent electron microscope - with coherence more than two orders of magnitude higher than that of a conventional electron microscope. So, electron beams split into components that pass through the middle and the outside would be expected to have a different phase. In such a magnet, the magnetic field is trapped inside, and no magnetic field exists either in the hole in through the middle or in the space outside the torus. One of the more remarkable experiments to demonstrate the Aharonov-Bohm (AB) effect was carried out by Akira Tonomura of Hitachi Laboratory in Japan, using microscopic toroidal (doughnut shaped) magnets. The effect was soon observed in experiments. Aharonov and Bohm predicted that, according to quantum theory - described by Schrödinger's wave function - the two beams, being wave-like, would acquire different phases due to their interaction with the vector potential, even though the field itself was zero, and that the difference between these phases could be detected via interference. Although the magnetic field is zero outside the solenoid, the vector potential associated with the field is not zero. The beam is split into two so that one passes to the left and the other to the right of the solenoid. In 1959, quantum physicists Yakir Aharonov and the late David Bohm at Birbeck College, London University, proposed a thought-experiment in which an electron beam is directed towards a long thin magnetic field trapped inside a tightly-wound coil of electric wire, a solenoid. In classical electromagnetic theory, the vector and scalar potentials in Maxwell's equations of the electromagnetic field are purely mathematical entities without physical significance, but not so in quantum mechanics. Mae-Wan Ho investigates the link between quantum phases and quantum coherence, and comes up with the surprising implication that the universe itself may be quantum coherent Quantum phases 13, 14 The sensitivity of quantum sensors, which is proportional to \(\frac\).Dr. ![]() 13 In quantum computers, in order to achieve quantum error correction, at least 10 4 quantum gate operations need to be performed within T 2, yielding a desired coherence time larger than 100 μs. 10, 11 The spin coherence time T 2, usually measured by Hahn-echo experiments, 12 is a critical property for qubit applications. 1 Defect-based solid-state spin qubits have been widely studied, including the nitrogen-vacancy (NV) center in diamond, 2, 3 vacancies in SiC, 4, 5, 6, 7 donor spins in silicon, 8 and rare-earth ions, 9 targeting quantum computing, and sensing applications. Deep-level defects in wide-bandgap semiconductors exhibit localized electronic energy levels with paramagnetic spin states, and hence they constitute promising platforms for quantum bits (qubits). ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |