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SUMMARY:Quantum control of magnon modes in ferromagnet - Nakamura\, Y (Tok
 yo University)
DTSTART:20140806T123000Z
DTEND:20140806T131000Z
UID:TALK53677@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Concepts and technologies of quantum coherent control were ini
 tially developed in microscopic systems such as atoms\, nuclear and electr
 on spins. However\, triggered by the emergence of quantum information scie
 nce\, they have recently been extended toward more macroscopic degrees of 
 freedom such as collective excitations in solid. The most pronounced examp
 le is electromagnetic excitations in superconducting circuits\, in which s
 uperconducting qubits have been realized by exploiting the nonlinearity pr
 ovided by Josephson junctions. The artificial two-level systems\, or atoms
 \, coupled with superconducting resonators and other quantum systems have 
 been enjoying rich physics and applications of circuit quantum electrodyna
 mics (circuit QED) and hybrid quantum systems.\n\nSpin-wave excitations (m
 agnons) in magnetic materials are another well-known collective excitation
  which is commonly studied in magnetism and spintronics. Sometimes they ha
 ve a long lifetime\, for example\, in the typical ferromagnetic insulator\
 , yttrium iron garnet (YIG). \n\nWe have investigated ferromagnetic resona
 nce of a mm-scale YIG sphere at low temperature (10 mK) and low power (-14
 0 dBm). The sphere is placed in a microwave cavity resonator made of oxyge
 n-free copper and biased with a static field of about 0.3 T. We demonstrat
 e coherent coupling between the magnon mode (the Kittel mode) with the mic
 rowave cavity mode (10 GHz)\, even in the quantum limit where both the ave
 rage magnon and photon numbers are less than one. \n\nWe also discuss how 
 to couple the magnon mode with a superconducting qubit via a resonator. Co
 herent coupling with a qubit enables quantum control and measurement of th
 e magnon excitations and thus opens a field of quantum magnonics. \n\nThis
  work was done in collaboration with Y. Tabuchi\, S. Ishino\, T. Ishikawa\
 , R. Yamazaki\, and K. Usami.\n
LOCATION:Seminar Room 1\, Newton Institute
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