Howard John Carmichael (born 17 January 1950) is a British-born New Zealand theoretical physicist specialising in
quantum optics
Quantum optics is a branch of atomic, molecular, and optical physics dealing with how individual quanta of light, known as photons, interact with atoms and molecules. It includes the study of the particle-like properties of photons. Photons have b ...
and the theory of open quantum systems.
He is the Dan Walls Professor of Physics at the
University of Auckland
, mottoeng = By natural ability and hard work
, established = 1883; years ago
, endowment = NZD $293 million (31 December 2021)
, budget = NZD $1.281 billion (31 December 2021)
, chancellor = Cecilia Tarrant
, vice_chancellor = Dawn F ...
and a principal investigator of the
Dodd-Walls Centre
The Dodd-Walls Centre for Photonic and Quantum Technologies () is a New Zealand Centre of Research Excellence, established in 2015, hosted by the University of Otago, and composed of researchers in six New Zealand universities as well as partn ...
. Carmichael has played a role in the development of the field of quantum optics and is particularly known for his
Quantum Trajectory Theory (QTT) which offers a more detailed view of quantum behaviour by making predictions of single events happening to individual quantum systems.
Carmichael works with experimental groups around the world to apply QTT to experiments on single quantum systems, including those contributing to the development of quantum computers.
He is a Fellow of
Optical Society of America
Optica (formerly known as The Optical Society (OSA) and before that as the Optical Society of America) is a professional society of individuals and companies with an interest in optics and photonics. It publishes journals and organizes conference ...
, the
American Physical Society
The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of k ...
and the
Royal Society of New Zealand
Royal may refer to:
People
* Royal (name), a list of people with either the surname or given name
* A member of a royal family
Places United States
* Royal, Arkansas, an unincorporated community
* Royal, Illinois, a village
* Royal, Iowa, a cit ...
. He was awarded the Max Born Award in 2003, the
Humboldt Research Award
The Humboldt Prize, the Humboldt-Forschungspreis in German, also known as the Humboldt Research Award, is an award given by the Alexander von Humboldt Foundation of Germany to internationally renowned scientists and scholars who work outside of G ...
in 1997 and the Dan Walls Medal of the New Zealand Institute of Physics in 2017. In 2015, he was recognised as an Outstanding Referee by the
American Physical Society
The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of k ...
.
Biography and education
Carmichael was born in Manchester England on January 17, 1950
and emigrated to New Zealand. He gained a
BSc
A Bachelor of Science (BS, BSc, SB, or ScB; from the Latin ') is a bachelor's degree awarded for programs that generally last three to five years.
The first university to admit a student to the degree of Bachelor of Science was the University ...
in physics and mathematics in 1971, and an MSc in physics in 1973 at the
University of Auckland
, mottoeng = By natural ability and hard work
, established = 1883; years ago
, endowment = NZD $293 million (31 December 2021)
, budget = NZD $1.281 billion (31 December 2021)
, chancellor = Cecilia Tarrant
, vice_chancellor = Dawn F ...
.
It was here that Carmichael met New Zealand physicist
Dan Walls
Daniel Frank Walls Fellow of the Royal Society, FRS (13 September 1942 – 12 May 1999) was a New Zealand theoretical physicist specialising in quantum optics.
Education
Walls gained a BSc in physics and mathematics and a first class honours M ...
, who supervised Carmichael's MSc in Auckland, and later his PhD at the
University of Waikato
The University of Waikato ( mi, Te Whare Wānanga o Waikato), is a Public university, public research university in Hamilton, New Zealand, Hamilton, New Zealand established in 1964. An additional campus is located in Tauranga.
The university perfo ...
from 1972 to 1977.
Having just returned from PhD and postdoctoral studies with Roy Glauber at Harvard University and Hermann Haken at the University of Stuttgart, Walls brought the rapidly growing field of Quantum Optics to New Zealand, established a major research centre with an active strategy of collaborating with quantum optics groups around the world.
During Carmichael's PhD studies, he and Walls made seminal contributions to the theoretical foundations of quantum optics.
He then travelled to the United States for further postgraduate studies.
After post-doctoral positions at the
City University of New York
The City University of New York ( CUNY; , ) is the Public university, public university system of Education in New York City, New York City. It is the largest urban university system in the United States, comprising 25 campuses: eleven Upper divis ...
, and at the
University of Texas at Austin
The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,075 ...
(1979–1981) Carmichael was appointed as an assistant professor and later associate professor at the
University of Arkansas
The University of Arkansas (U of A, UArk, or UA) is a public land-grant research university in Fayetteville, Arkansas. It is the flagship campus of the University of Arkansas System and the largest university in the state. Founded as Arkansas ...
. He was a visiting scientist at the
Royal Signal and Radar Establishment in
Malvern
Malvern or Malverne may refer to:
Places Australia
* Malvern, South Australia, a suburb of Adelaide
* Malvern, Victoria, a suburb of Melbourne
* City of Malvern, a former local government area near Melbourne
* Electoral district of Malvern, an e ...
in 1984, visiting professor at the
University of Texas at Austin
The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,075 ...
in 1988 and at
Caltech
The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...
in 1989. In 1989 he was made associate professor, and in 1991 full professor, at the
University of Oregon
The University of Oregon (UO, U of O or Oregon) is a public research university in Eugene, Oregon. Founded in 1876, the institution is well known for its strong ties to the sports apparel and marketing firm Nike, Inc, and its co-founder, billion ...
.
He returned to New Zealand in 2002
to join the
University of Auckland
, mottoeng = By natural ability and hard work
, established = 1883; years ago
, endowment = NZD $293 million (31 December 2021)
, budget = NZD $1.281 billion (31 December 2021)
, chancellor = Cecilia Tarrant
, vice_chancellor = Dawn F ...
, becoming the inaugural Dan Walls Professor of Physics, a position he still holds today.
Research
Carmichael has made seminal contributions to the field of quantum optics and open quantum systems over more than four decades.
He is known particularly for his development of quantum trajectory theory (1993), which offers a way to describe the evolution of a quantum system as it interacts with its environment.
In 1993 he developed (at the same time as a separate formulation by
Crispin Gardiner
Crispin William Gardiner (born 18 October 1942 in Hastings New Zealand) is a New Zealand physicist, who has worked in the fields of Quantum Optics, Ultracold Atoms and Stochastic Processes. He has written about 120 journal articles and sever ...
) the theory and application of
cascaded quantum systems, in which the optical output of one quantum system becomes the optical input for another quantum system.
He has also contributed to advances in the theory of
nonclassical light
Nonclassical light is light that cannot be described using classical electromagnetism; its characteristics are described by the quantized electromagnetic field and quantum mechanics.
The most common described forms of nonclassical light are the fo ...
and
quantum correlation In quantum mechanics, quantum correlation is the expected value of the product of the alternative outcomes. In other words, it is the expected change in physical characteristics as one quantum system passes through an interaction site. In John Be ...
,
quantum optical measurements,
quantum fluctuation
In quantum physics, a quantum fluctuation (also known as a vacuum state fluctuation or vacuum fluctuation) is the temporary random change in the amount of energy in a point in space, as prescribed by Werner Heisenberg's uncertainty principle. ...
s and noise in
radiative process
In particle physics, a radiative process refers to one elementary particle emitting another and continuing to exist. This typically happens when a fermion emits a boson such as a gluon or photon.
See also
*Bremsstrahlung
''Bremsstrahlun ...
es,
nonlinear
In mathematics and science, a nonlinear system is a system in which the change of the output is not proportional to the change of the input. Nonlinear problems are of interest to engineers, biologists, physicists, mathematicians, and many other ...
physics and multi-photon processes,
cavity quantum electrodynamics Cavity quantum electrodynamics (cavity QED) is the study of the interaction between light confined in a reflective cavity and atoms or other particles, under conditions where the quantum nature of photons is significant. It could in principle be u ...
,
quantum statistical methods and
quantum entanglement
Quantum entanglement is the phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of ...
.
Antibunched light
In 1976, while Carmichael was still a graduate student, he and his doctoral supervisor
Dan Walls
Daniel Frank Walls Fellow of the Royal Society, FRS (13 September 1942 – 12 May 1999) was a New Zealand theoretical physicist specialising in quantum optics.
Education
Walls gained a BSc in physics and mathematics and a first class honours M ...
published a seminal paper
that predicted
photon antibunching
Photon antibunching generally refers to a light field with photons more equally spaced than a coherent laser field, a signature being signals at appropriate detectors which are anticorrelated. More specifically, it can refer to sub-Poissonian ph ...
, which led to the experimental demonstration of the quantum nature of light.
The paper was based on their work with
master equation
In physics, chemistry and related fields, master equations are used to describe the time evolution of a system that can be modelled as being in a probabilistic combination of states at any given time and the switching between states is determine ...
techniques to describe
open quantum system In physics, an open quantum system is a quantum-mechanical system that interacts with an external quantum system, which is known as the ''environment'' or a ''bath''. In general, these interactions significantly change the dynamics of the system an ...
s, which Carmichael began during his masters. They had decided to investigate
resonance fluorescence
Resonance fluorescence is the process in which a two-level atom system interacts with the quantum electromagnetic field if the field is driven at a frequency near to the natural frequency of the atom.
General theory
Typically the photon contai ...
because it seemed like a good application of their master equations to two coupled
open quantum system In physics, an open quantum system is a quantum-mechanical system that interacts with an external quantum system, which is known as the ''environment'' or a ''bath''. In general, these interactions significantly change the dynamics of the system an ...
s. There was considerable international interest among the fledgling quantum optics community, in both experimental and theoretical
resonance fluorescence
Resonance fluorescence is the process in which a two-level atom system interacts with the quantum electromagnetic field if the field is driven at a frequency near to the natural frequency of the atom.
General theory
Typically the photon contai ...
.
Using their newly developed master equation techniques, Walls and Carmichael derived the form of the fluorescence spectrum that agreed with previous experimental results. They went on to calculate the second-order
correlation function
A correlation function is a function that gives the statistical correlation between random variables, contingent on the spatial or temporal distance between those variables. If one considers the correlation function between random variables rep ...
to explore the statistics of resonance fluorescence. They were able to use the correlation function to explain how jumps of an emitting atom imprint on the emitted photon stream. They predicted that the correlation function should drop to zero at zero time delay and suggested a Quantum Electrodynamics (QED) experiment to test their predictions. These experiments were performed shortly afterwards providing evidence of the quantum character of the light emitted in resonance fluorescence.
Quantum trajectory theory (QTT)
Carmichael developed quantum trajectory theory (QTT) in the early 1990s,
around the same time as the separate formulations by
Dalibard Castin & Mølmer, and by
Zoller,
Ritsch & Dum). QTT (also known as
quantum jump method or
Monte Carlo
Monte Carlo (; ; french: Monte-Carlo , or colloquially ''Monte-Carl'' ; lij, Munte Carlu ; ) is officially an administrative area of the Principality of Monaco, specifically the ward of Monte Carlo/Spélugues, where the Monte Carlo Casino is ...
wave function (MCWF)) is a formulation of quantum mechanics that tracks the path that a quantum object takes through the space of all its possible states as it is measured.
QTT is compatible with the standard formulation of quantum theory, as described by the
Schrödinger equation
The Schrödinger equation is a linear partial differential equation that governs the wave function of a quantum-mechanical system. It is a key result in quantum mechanics, and its discovery was a significant landmark in the development of the ...
, but offers a more detailed view.
The
Schrödinger equation
The Schrödinger equation is a linear partial differential equation that governs the wave function of a quantum-mechanical system. It is a key result in quantum mechanics, and its discovery was a significant landmark in the development of the ...
, is a probabilistic theory. It gives the probability of finding a quantum system in each of its possible states should a measurement be made. This is useful for predicting average measurements of large ensembles of quantum objects but it does not describe the behaviour of individual particles. QTT fills this gap by offering a way to describe the trajectories of individual quantum particles that obey the probabilities given by the Schrödinger equation.
QTT also works with
open quantum system In physics, an open quantum system is a quantum-mechanical system that interacts with an external quantum system, which is known as the ''environment'' or a ''bath''. In general, these interactions significantly change the dynamics of the system an ...
s that interact with their environment unlike the Schrödinger equation which only describes a quantum system in isolation.
QTT has become particularly popular since the technology has become available to efficiently control and monitor individual quantum systems as it can predict how individual quantum objects such as particles will behave when they are observed.
In QTT
open quantum system In physics, an open quantum system is a quantum-mechanical system that interacts with an external quantum system, which is known as the ''environment'' or a ''bath''. In general, these interactions significantly change the dynamics of the system an ...
s are modelled as
scattering
Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...
processes, with classical external fields corresponding to the inputs and classical
stochastic process
In probability theory and related fields, a stochastic () or random process is a mathematical object usually defined as a family of random variables. Stochastic processes are widely used as mathematical models of systems and phenomena that appea ...
es corresponding to the outputs (the fields after the measurement process).
The mapping from inputs to outputs is provided by a quantum
stochastic
Stochastic (, ) refers to the property of being well described by a random probability distribution. Although stochasticity and randomness are distinct in that the former refers to a modeling approach and the latter refers to phenomena themselv ...
process that is set up to account for a particular measurement strategy (eg.,
photon counting
Photon counting is a technique in which individual photons are counted using a single-photon detector (SPD). A single-photon detector emits a pulse of signal for each detected photon, in contrast to a normal photodetector, which generates an analo ...
,
homodyne
In electrical engineering, homodyne detection is a method of extracting information encoded as modulation of the phase and/or frequency of an oscillating signal, by comparing that signal with a standard oscillation that would be identical to the ...
/
heterodyne
A heterodyne is a signal frequency that is created by combining or mixing two other frequencies using a signal processing technique called ''heterodyning'', which was invented by Canadian inventor-engineer Reginald Fessenden. Heterodyning is u ...
detection, etc).
QTT addresses the
measurement problem
In quantum mechanics, the measurement problem is the problem of how, or whether, wave function collapse occurs. The inability to observe such a collapse directly has given rise to different interpretations of quantum mechanics and poses a key se ...
in quantum mechanics by providing a detailed description of what happens during the so-called "
collapse of the wave function
In quantum mechanics, wave function collapse occurs when a wave function—initially in a superposition of several eigenstates—reduces to a single eigenstate due to interaction with the external world. This interaction is called an ''observat ...
". It reconciles the concept of a
quantum jump with the smooth evolution described by the
Schrödinger equation
The Schrödinger equation is a linear partial differential equation that governs the wave function of a quantum-mechanical system. It is a key result in quantum mechanics, and its discovery was a significant landmark in the development of the ...
. The theory suggests that "quantum jumps" are not instantaneous but happen in a coherently driven system as a smooth transition through a series of
superposition states.
This prediction was tested experimentally in 2019 by a team at
Yale University
Yale University is a private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and among the most prestigious in the wo ...
led by
Michel Devoret
Michel Devoret is a French physicist and F. W. Beinecke Professor of Applied Physics at Yale University. He also holds a position as the Director of the Applied Physics Nanofabrication Lab at Yale. He is known for his pioneering work on macroscopi ...
and
Zlatko Minev in collaboration with Carmichael and others at
Yale University
Yale University is a private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and among the most prestigious in the wo ...
and the
University of Auckland
, mottoeng = By natural ability and hard work
, established = 1883; years ago
, endowment = NZD $293 million (31 December 2021)
, budget = NZD $1.281 billion (31 December 2021)
, chancellor = Cecilia Tarrant
, vice_chancellor = Dawn F ...
. In their experiment they used a
superconducting
Superconductivity is a set of physical properties observed in certain materials where Electrical resistance and conductance, electrical resistance vanishes and magnetic field, magnetic flux fields are expelled from the material. Any material e ...
artificial atom
Quantum dots (QDs) are semiconductor particles a few nanometres in size, having optical and electronic properties that differ from those of larger particles as a result of quantum mechanics. They are a central topic in nanotechnology. When the q ...
to observe a quantum jump in detail, confirming that the transition is a continuous process that unfolds over time. They were also able to detect when a quantum jump was about to occur and intervene to reverse it, sending the system back to the state in which it started.
This experiment, inspired and guided by QTT, represents a new level of control over quantum systems and has potential applications in correcting errors in quantum computing in the future.
Books
* Howard Carmichael (1999, 2002) ''An Open Systems Approach to Quantum Optics 1''; Springer, Berlin Heidelberg ( )
* H J Carmichael (1999, 2002
''Statistical Methods in Quantum Optics 1: Master Equations and Fokker‐Planck Equations'' Springer, Berlin Heidelberg ( )
* H J Carmichael (2008
''Statistical Methods in Quantum Optics 2: Non-Classical Fields'' Springer, Berlin Heidelberg ( )
* H J Carmichael, R J Glauber and M O Scully (Eds) (2001) ''Directions in Quantum Optics''; Springer, Berlin Heidelberg ()
Honours and awards
* Dan Walls Medal of the New Zealand
Institute of Physics
The Institute of Physics (IOP) is a UK-based learned society and professional body that works to advance physics education, research and application.
It was founded in 1874 and has a worldwide membership of over 20,000. The IOP is the Physica ...
(2017)
* Fellow of the
Royal Society of New Zealand
Royal may refer to:
People
* Royal (name), a list of people with either the surname or given name
* A member of a royal family
Places United States
* Royal, Arkansas, an unincorporated community
* Royal, Illinois, a village
* Royal, Iowa, a cit ...
(2006)
* The
Max Born Award
The Max Born Award is given by the Optical Society (formerly the Optical Society of America) for "outstanding contributions to physical optics", and is named after Max Born.
Recipients
SourceThe Optical Society
* 2022 Yuri Kivshar
* 2021 Anne L ...
of the
Optical Society of America
Optica (formerly known as The Optical Society (OSA) and before that as the Optical Society of America) is a professional society of individuals and companies with an interest in optics and photonics. It publishes journals and organizes conference ...
(2003)
*
Humboldt Research award
The Humboldt Prize, the Humboldt-Forschungspreis in German, also known as the Humboldt Research Award, is an award given by the Alexander von Humboldt Foundation of Germany to internationally renowned scientists and scholars who work outside of G ...
for Senior United States Scientists, Alexander Humboldt Foundation (1997)
* Fellow of the
American Physical Society
The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of k ...
(1995)
* Fellow of the
Optical Society of America
Optica (formerly known as The Optical Society (OSA) and before that as the Optical Society of America) is a professional society of individuals and companies with an interest in optics and photonics. It publishes journals and organizes conference ...
(1990)
References
{{DEFAULTSORT:Carmichael, Howard
1950 births
Living people
Optical physicists
Quantum physicists
Theoretical physicists
New Zealand physicists
University of Auckland alumni
Fellows of the American Physical Society
Fellows of Optica (society)
Fellows of the Royal Society of New Zealand