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駒場生の皆さん、物理工学科へぜひお越しください。

駒場生の皆さん、物理工学科へぜひお越しください。

  • 2018年度 進学ガイダンスブックダウンロードはこちら
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  • お知らせ
  • 談話会・セミナー
  • 教員公募のお知らせ(応募締切:2018/8/15)
    2018.07.17
  •  
  • 物理工学専攻では、このたび准教授1名を公募いたします。本公募の詳細についてはこちらをご覧ください。

  • 第3回 物理工学科教室談話会(講師:Prof. (Emeritus) Yoshihisa Yamamoto)
    2018.07.25
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  • 日時:2018年 9月6日(木),7日(金) 10:00 -12:00
    場所:工学部6号館2階62号室
    講師:Prof. (Emeritus) Yoshihisa Yamamoto
    所属:Department of Applied Physics, Stanford University ImPACT Program Manager, Japan Science and Technology Agency
    題目:Physics of quantum-to-classical crossover and coherent Ising machines;
    概要:
    The quantum computational model based on unitary rotation of state vectors in a closed system was proposed in mid-1980s. Feasibility of developing a practical computer based on this concept is still elusive in spite of world-wide research efforts over the past thirty years. In the beginning of the 21 century, a new concept of dissipative quantum computation utilizing quantum-to-classical crossover in an open-dissipative system emerged as an alternative approach to practical quantum computers. In this lecture, we will review the basic concept, theoretical methods and state of the art in experimental implementation of a particular machine, called coherent Ising machine, along this new direction.

    Day 1 topics: Gate-based quantum computation vs. network-based quantum computation, optical delay line coupling CIM vs. measurement feedback coupling CIM, squeezing and spontaneous symmetry breaking in optical parametric oscillators, natural phase error correction, state reduction induced by approximate homodyne measurements, quantum parallel search assisted by non-Gaussian wave-packets, benchmark against modern digital computers, QNN cloud system.

    Day 2 topics: Quantum theory of CIM, measurement-feedback master equation, positive P representation vs. truncated Wigner representation of density operators, c-number stochastic differential equations, replicator dynamics, Gaussian approximation, standard quantum limit and beyond in CIM, einselection and coherent states as unique pointer basis, quantum Darwinism and quantum-to-classical crossover in non-equilibrium systems.

    紹介教員:永長 直人 教授、樽茶 清悟 教授

お知らせ
  • 教員公募のお知らせ(応募締切:2018/8/15)
    2018.07.17
  •  
  • 物理工学専攻では、このたび准教授1名を公募いたします。本公募の詳細についてはこちらをご覧ください。

  • 教員公募のお知らせ(応募締切:2018/8/29)
    2018.06.29
  •  
  • 量子相エレクトロニクス研究センターでは、このたび特任准教授または特任講師を公募いたします。
    本公募の詳細についてはこちらをご覧ください。

もっと詳しく

談話会・セミナー
  • 第3回 物理工学科教室談話会(講師:Prof. (Emeritus) Yoshihisa Yamamoto)
    2018.07.25
  •  
  • 日時:2018年 9月6日(木),7日(金) 10:00 -12:00
    場所:工学部6号館2階62号室
    講師:Prof. (Emeritus) Yoshihisa Yamamoto
    所属:Department of Applied Physics, Stanford University ImPACT Program Manager, Japan Science and Technology Agency
    題目:Physics of quantum-to-classical crossover and coherent Ising machines;
    概要:
    The quantum computational model based on unitary rotation of state vectors in a closed system was proposed in mid-1980s. Feasibility of developing a practical computer based on this concept is still elusive in spite of world-wide research efforts over the past thirty years. In the beginning of the 21 century, a new concept of dissipative quantum computation utilizing quantum-to-classical crossover in an open-dissipative system emerged as an alternative approach to practical quantum computers. In this lecture, we will review the basic concept, theoretical methods and state of the art in experimental implementation of a particular machine, called coherent Ising machine, along this new direction.

    Day 1 topics: Gate-based quantum computation vs. network-based quantum computation, optical delay line coupling CIM vs. measurement feedback coupling CIM, squeezing and spontaneous symmetry breaking in optical parametric oscillators, natural phase error correction, state reduction induced by approximate homodyne measurements, quantum parallel search assisted by non-Gaussian wave-packets, benchmark against modern digital computers, QNN cloud system.

    Day 2 topics: Quantum theory of CIM, measurement-feedback master equation, positive P representation vs. truncated Wigner representation of density operators, c-number stochastic differential equations, replicator dynamics, Gaussian approximation, standard quantum limit and beyond in CIM, einselection and coherent states as unique pointer basis, quantum Darwinism and quantum-to-classical crossover in non-equilibrium systems.

    紹介教員:永長 直人 教授、樽茶 清悟 教授

  • もっと詳しく
  • 第2回 物理工学科教室談話会(講師:Prof. Yasutomo J. Uemura)
    2018.07.12
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  • 日時 2018年7月18日(水) 午後4時
    講師 Prof. Yasutomo J. Uemura
    所属 Columbia University
    題目 Onset of the photo-excited transient superconductivity and Nernst effect at the emergence of local phase coherence of preformed pairs
    場所 大会議室

    In recent series of optical conductivity measurements after ultrafast laser photo-excitations in high-Tc cuprates and K3C60 systems, Cavalleri and co-workers found a signature similar to superconducting gapping in transient responses well above Tc, reaching up to 300–400K[1,2]. In 2000–2010, Ong and co-workers observed Nernst effect [3] and diamagnetic susceptibility [4] which develop in the underdoped region of cuprates well above Tc. In this presentation, resorting to a plot of Tc versus the superfluid density [5], and Tc versus the effective Fermi temperature TF [5,6], we point out that the onset of the transient gapping of optical conductivity, Nernst effect and diamagnetic susceptibility occurs at the emergence of local phase coherence of preformed pairs in the normal state well above Tc.

    Since 1988, we performed Muon Spin Relaxation measurements of the superfluid density ns/m* in high Tc cuprate and many other unconventional superconductors [4], and presented a nearly linear relation between Tc and ns/m* at T → 0, and Tc vs TF obtained from ns/m*. The superfluid density corresponds to the gapped Drude spectral weight in optical conductivity.
    From ns/m* one can derive a “hypothetical BEC energy scale” TBEC by calculating Bose-Einstein condensation temperature of ideal non-interacting Bose gas having boson density of ns/2 and mass 2m*. TBEC represents the temperature at which the thermal wave length of bosons becomes comparable to the interboson distance. For the situation with dominant pre-formed pairs in the normal state of underdoped cuprates, superconductivity should have occurred at TBEC if there were no competing states.
    The actual Tc in cuprates and other unconventional superconductors is reduced from TBEC at least by a factor of 4-5 due to competition of superconducting (SC) and antiferromagnetic (AF) order. In strongly underdoped region of cuprates, however, we demonstrate that TBEC derived from MuSR agrees well with the onset temperature of Nernst effect and the diamagnetic susceptibility, and TBEC derived from the transient gapped spectral weight of optical responses agrees well with the onset temperature of the gapped optical responses.
    This observation can be extended to the cases in K3C60, organic BEDT superconductors, as well as URu2Si2. These results suggest that the “superconductivity-like” responses in Nernst, diamagnetic and transient optical conductivity measurements emerge when local, dynamic and short-ranged phase coherence develop among pre-formed pairs. We also discuss the role of the magnetic resonance mode which controls Tc in the competition of the SC and AF orders, resorting to an analogy with rotons in superfluid 4He [6] and noticing a transient loss of the 400 cm-1 mode responses
    in photo-excited optical conductivity [7].

    References
    [1] D. Fausti, et al., Science 331, 189 (2011); C.R. Hunt et al., Phys. Rev, B94, 224303 (2016).
    [2] M. Mitrano et al., Nature 530, 461 (2016); A. Cantaluppi et al., Nature Physics, in press.
    [3] Z. A. Xu et al., Nature 406, 486 (2000); Y. Wang et al., Phys. Rev. B73, 024510 (2006).
    [4] Y. Wang et al., PRL 95, 247002 (2005); L. Li et al., Phys. Rev. B81, 054510 (2010)
    [5] Y. J. Uemura, et al., PRL 62, 2317 (1989); PRL 66, 2665 (1991).
    [6] Y. J. Uemura, J. Phys. Condens. Matter 16, S4515 (2004); Nature Materials 8, 253 (2009)
    [7] W.Hu et al., Phys. Rev. B95, 104508 (2017).

    紹介教員 山地洋平 准教授、今田正俊 教授

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