珞珈山水BBS -- 单文区文章阅读

搜索

单文区文章阅读 [返回]
发信人: leader (kikizh), 信区: Physics 标题: Re: 光子只与自己干涉吗？发信站: BBS 珞珈山水站 (Sat Mar 8 17:14:28 2008) Obituary: Leonard Mandel (1927–2001) G. S. Agarwal1 and Z. Y. Ou2 Pioneer in quantum approaches to light Leonard Mandel, one of the founding fathers of quantum optics, died at his hom e on 9 February at the age of 73. Our generation of optical scientists grew up learning from Mandel's work: quite literally, he showed us the light by openi ng up many new avenues of research. He was an elegant experimentalist and a ce lebrated theorist. Echoes of his unmistakable slow but clear voice will contin ue to remind us of the contributions of this remarkable man. Mandel was born in Berlin, but moved to Britain when he was a boy. He was educ ated at the University of London, studying cosmic rays for his PhD, which was awarded in 1951. After a short spell in industry, Mandel took up an academic p ost at Imperial College, London. It was the investigation of cosmic rays that eventually led him to discover what is today known as Mandel's photon-counting formula, which relates the statistical properties of arbitrary optical fields to those of photoelectrons detected experimentally. Mandel worked throughout his career to perfect the photon-counting technique for studying a variety of optical fields, from the thermal light of a candle to sophisticated quantum so urces. In the 1960s, this work enabled physicists to understand the statistica l properties of lasers operating under different pumping conditions. Such stud ies gave support to the quantum theory of the laser. Mandel performed his first major experiment at Imperial, its simplicity in des ign becoming one of his trademarks. The result, typically, was counterintuitiv e. The experiment showed how interference between independent photon beams can be observed and that such a possibility is permitted by quantum physics. His demonstration of two-photon interference followed. This was an experiment that laid the foundation for later work on quantum entanglement, a concept of stat e superposition first introduced by Erwin Schrödinger. In 1964 Mandel settled permanently in Rochester, New York, having been persuad ed to move there by Emil Wolf. Wolf and Mandel wrote several notable papers to gether, and also organized the Rochester Conferences on Quantum Optics, which laid the foundations of the field and continue to this day. It was at one of t he early conferences that debate really began to heat up on the need for a qua ntum theory of light, and Mandel started to devote much of his research to sea rching for the subtle differences between the classical and quantum descriptio ns of light. Applying a mixture of theory and experiment, Mandel and colleagues revealed se veral uniquely quantum-mechanical properties of light. In 1977, for instance, his group observed the 'photon anti-bunching' effect, in which photons from a single two-level atom illuminated by a resonant laser can never be emitted in pairs or more, providing confirmation of a 'quantum jump'. This was followed b y the demonstration of sub-poissonian photon statistics, which mean that fluct uations in the photon number of an optical field are smaller than would be exp ected for random events, such as the fall of raindrops. These were the first r eported observations of 'non-classicality' requiring a full quantum descriptio n of light, and they changed our perspective on light. Photon interference was the hallmark of Mandel's work. In the 1980s his group carried out a series of ground-breaking yet ingeniously simple experiments to demonstrate the quantum entanglement of photons and, subsequently, the non-loc ality of quantum mechanics through violations of Bell's inequalities in the Ei nstein–Podolsky–Rosen paradox. These studies set the ball rolling for a larg e number of experiments world wide dealing with the foundations of quantum mec hanics, and for newer developments such as quantum teleportation, quantum encr yption, and cryptography for quantum-information processing. As he entered his seventh decade, Mandel was still as productive as ever in ad dressing some of the fundamentals of physics. One of the problems that bothere d Paul Dirac, the founder of quantum electrodynamics, was how to define the ph ase of a quantized electromagnetic field: phase is crucial in understanding al l interference phenomena. The answer remained elusive until the early 1990s, w hen Mandel introduced the concept of measurable phase, and actually measured t he phase characteristics of a quantized field. In this same period he demonstrated the non-existence of a pilot wave, which i s at the heart of de Broglie's wave interpretation of quantum mechanics. And i n another conceptually straightforward but mind-boggling experiment, Mandel an d his students demonstrated the complementarity of light — that is, its behav iour as either a wave or a particle in different circumstances. It was, of cou rse, known that placing a detector in its path could change the behaviour of l ight. But Mandel found that an experimental set up that merely has the possibi lity of making a measurement, even if only in principle, could bring that chan ge about: no actual measurement is required. Mandel was a private but generous person. Discussions with him were invariably inspiring, often leading to fresh ideas, as we ourselves can attest. Although his voice was weakened by illness, Mandel's mind remained as sharp as ever. O nly a few months before his death, he and his colleagues published a paper on squeezing the quantum noise in atomic spin, an approach which may lead to enta ngled states of atoms. As well as being a world-class researcher, Mandel was a great teacher. Many of his 39 PhD students became leaders in their fields: Jeff Kimble, for instance , with whom Mandel discovered the photon anti-bunching effect, is working at t he forefront of the new field of quantum information science, which is based o n the concept of quantum entanglement. The field that Mandel opened up, and to which he made so many contributions, has begun to have an impact on the infor mation age in which we now live. His legacy is to have provided the inspiratio n for the next generation of researchers pursuing a deeper understanding of th e fundamental laws of nature and their applications. 【在 leader (kikizh) 的大作中提到: 】 : dirac对量子力学的建立贡献很大，有本量子力学被誉为Bible，反正我师弟整个研一.. : 不看，就看那个了。 : 不过任何人都可能犯错，都会受时代的局限。dirac的量子力学里有个很了不起的错�.. : ................... -- 有限的生命，只读经典的文章 limited life for classic papers ※ 来源:·珞珈山水BBS站 http://bbs.whu.edu.cn·[FROM: 159.226.37.*]
[返回单文区目录]

单文区文章阅读 [返回]

发信人: leader (kikizh), 信区: Physics
标  题: Re: 光子只与自己干涉吗？
发信站: BBS 珞珈山水站 (Sat Mar  8 17:14:28 2008)

Obituary:  Leonard Mandel (1927–2001)
G. S. Agarwal1 and Z. Y. Ou2

Pioneer in quantum approaches to light
Leonard Mandel, one of the founding fathers of quantum optics, died at his hom
e on 9 February at the age of 73. Our generation of optical scientists grew up
learning from Mandel's work: quite literally, he showed us the light by openi
ng up many new avenues of research. He was an elegant experimentalist and a ce
lebrated theorist. Echoes of his unmistakable slow but clear voice will contin
ue to remind us of the contributions of this remarkable man.

Mandel was born in Berlin, but moved to Britain when he was a boy. He was educ
ated at the University of London, studying cosmic rays for his PhD, which was
awarded in 1951. After a short spell in industry, Mandel took up an academic p
ost at Imperial College, London. It was the investigation of cosmic rays that
eventually led him to discover what is today known as Mandel's photon-counting
formula, which relates the statistical properties of arbitrary optical fields
to those of photoelectrons detected experimentally. Mandel worked throughout
his career to perfect the photon-counting technique for studying a variety of
optical fields, from the thermal light of a candle to sophisticated quantum so
urces. In the 1960s, this work enabled physicists to understand the statistica
l properties of lasers operating under different pumping conditions. Such stud
ies gave support to the quantum theory of the laser.

Mandel performed his first major experiment at Imperial, its simplicity in des
ign becoming one of his trademarks. The result, typically, was counterintuitiv
e. The experiment showed how interference between independent photon beams can
be observed and that such a possibility is permitted by quantum physics. His
demonstration of two-photon interference followed. This was an experiment that
laid the foundation for later work on quantum entanglement, a concept of stat
e superposition first introduced by Erwin Schrödinger.

In 1964 Mandel settled permanently in Rochester, New York, having been persuad
ed to move there by Emil Wolf. Wolf and Mandel wrote several notable papers to
gether, and also organized the Rochester Conferences on Quantum Optics, which
laid the foundations of the field and continue to this day. It was at one of t
he early conferences that debate really began to heat up on the need for a qua
ntum theory of light, and Mandel started to devote much of his research to sea
rching for the subtle differences between the classical and quantum descriptio
ns of light.

Applying a mixture of theory and experiment, Mandel and colleagues revealed se
veral uniquely quantum-mechanical properties of light. In 1977, for instance,
his group observed the 'photon anti-bunching' effect, in which photons from a
single two-level atom illuminated by a resonant laser can never be emitted in
pairs or more, providing confirmation of a 'quantum jump'. This was followed b
y the demonstration of sub-poissonian photon statistics, which mean that fluct
uations in the photon number of an optical field are smaller than would be exp
ected for random events, such as the fall of raindrops. These were the first r
eported observations of 'non-classicality' requiring a full quantum descriptio
n of light, and they changed our perspective on light.

Photon interference was the hallmark of Mandel's work. In the 1980s his group
carried out a series of ground-breaking yet ingeniously simple experiments to
demonstrate the quantum entanglement of photons and, subsequently, the non-loc
ality of quantum mechanics through violations of Bell's inequalities in the Ei
nstein–Podolsky–Rosen paradox. These studies set the ball rolling for a larg
e number of experiments world wide dealing with the foundations of quantum mec
hanics, and for newer developments such as quantum teleportation, quantum encr
yption, and cryptography for quantum-information processing.

As he entered his seventh decade, Mandel was still as productive as ever in ad
dressing some of the fundamentals of physics. One of the problems that bothere
d Paul Dirac, the founder of quantum electrodynamics, was how to define the ph
ase of a quantized electromagnetic field: phase is crucial in understanding al
l interference phenomena. The answer remained elusive until the early 1990s, w
hen Mandel introduced the concept of measurable phase, and actually measured t
he phase characteristics of a quantized field.

In this same period he demonstrated the non-existence of a pilot wave, which i
s at the heart of de Broglie's wave interpretation of quantum mechanics. And i
n another conceptually straightforward but mind-boggling experiment, Mandel an
d his students demonstrated the complementarity of light — that is, its behav
iour as either a wave or a particle in different circumstances. It was, of cou
rse, known that placing a detector in its path could change the behaviour of l
ight. But Mandel found that an experimental set up that merely has the possibi
lity of making a measurement, even if only in principle, could bring that chan
ge about: no actual measurement is required.

Mandel was a private but generous person. Discussions with him were invariably
inspiring, often leading to fresh ideas, as we ourselves can attest. Although
his voice was weakened by illness, Mandel's mind remained as sharp as ever. O
nly a few months before his death, he and his colleagues published a paper on
squeezing the quantum noise in atomic spin, an approach which may lead to enta
ngled states of atoms.

As well as being a world-class researcher, Mandel was a great teacher. Many of
his 39 PhD students became leaders in their fields: Jeff Kimble, for instance
, with whom Mandel discovered the photon anti-bunching effect, is working at t
he forefront of the new field of quantum information science, which is based o
n the concept of quantum entanglement. The field that Mandel opened up, and to
which he made so many contributions, has begun to have an impact on the infor
mation age in which we now live. His legacy is to have provided the inspiratio
n for the next generation of researchers pursuing a deeper understanding of th
e fundamental laws of nature and their applications.

【在 leader (kikizh) 的大作中提到: 】
: dirac对量子力学的建立贡献很大，有本量子力学被誉为Bible，反正我师弟整个研一..
: 不看，就看那个了。
: 不过任何人都可能犯错，都会受时代的局限。dirac的量子力学里有个很了不起的错�..
: ...................

--
有限的生命，只读经典的文章

limited life for classic papers

※ 来源:·珞珈山水BBS站

http://bbs.whu.edu.cn·[FROM: 159.226.37.*]

[返回单文区目录]