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Subtle Agroecologies
complementarity. According to the Copenhagen interpretation of quantum mechanics, all the information about a particle or a system of particles can thus be described in a wave-like manner that
is denoted mathematically by a wave function, ϕ(x, t). However, wave functions behave like waves
and can diffract, and interfere together forming superpositions, implying that quantum particles
simultaneously exist in multiple spatial locations and states. When a measurement is made, one of
the multiple states is chosen and the quantum superposition of states ends being reduced to a classical state in a process known as the collapse of the wave function.
While quantum mechanics was developed with elementary particles in mind, its subsequent
applications extended its validity to systems of many particles such as those encountered in condensed matter physics, e.g. in the description of the conduction electron ‘sea’, excitons, magnons,
polarons, polaritons, etc. These types of quantum properties of macroscopic physical systems
are called collective excitations. A system of many particles under specifc conditions cannot
be separated into individual wave functions for each particle; rather, the system is described
by a single wave function describing its collective behaviour. This physical property is called
quantum coherence, and it is characterised by individual particles losing their separate identities
so that the entire system acts as a whole. Particles that were once unifed in a common quantum
state remain physically connected even at a distance. As a consequence of the collective behaviour of many-body systems, hallmarks of quantum mechanics can be seen in the properties of
macroscopic objects such as crystals or ferromagnets, even above room temperature. There are
also more exotic direct manifestations of quantum behaviour in macroscopic systems such as
superconductors (with no measurable resistance to electrical current and ideal diamagnetism) or
superfuids (with no viscosity and infnite vorticity). However, these latter two examples have so
far been limited to very low temperatures. The precise location of the boundary (in terms of both
the object’s size and ambient temperature) between quantum and classical regimes is still under
debate.
FROM QUANTUM CHEMISTRY TO QUANTUM BIOLOGY
Extensions of quantum mechanics to chemical compounds and chemical reactions proved to be
exceedingly successful, and an entire feld of quantum chemistry was developed as a consequence.
In order to understand the creation of chemical bonds, especially covalent bonds in which electrons
are shared between atoms of a molecule, a quantum mechanical wave function was introduced into
the formalism as one of the postulates of quantum mechanics. All chemistry, including biochemistry, is based on the creation and destruction of bonds between atoms and hence on quantum interactions. Hence, by extension the structural stability of all living systems, like non-living systems,
depends on quantum states at the level of chemical bonds. However, the quantum effects are commonly claimed to be washed out due to decoherence taking place at scales larger than individual
atoms or sub-atomic particles, at higher temperatures and in aqueous media, which provide a noisy
environment for particle interactions. Thus, the likelihood of quantum states playing functional
roles at macroscopic scales in ‘warm, wet and noisy’ biological systems seems problematic due
to environmental decoherence effects. On the other hand, it is reasonable to expect that evolution,
through the process of natural selection over billions of years of experimentation and countless parallel attempts of trial and error, may have solved the decoherence problem so that quantum states
may be essential features of biological systems (Rosa and Faber, 2004).
Erwin Schrödinger, Niels Bohr, Werner Heisenberg, Eugene Wigner and their contemporaries
all offered speculations about quantum effects in living systems, while Schrödinger’s famous book
What Is Life? (Schrödinger, 1944) actually paved the way for the birth of molecular biology in the
1950s. What is still very much a mystery, however, is the perfect synchronisation of biological processes across spatial and temporal dimensions that connect the hierarchical organisational scales of
a living system. Here, quantum mechanics may indeed come to the rescue, if only we could explain
the required absence of decoherence.
Subtle Agroecologies
complementarity. According to the Copenhagen interpretation of quantum mechanics, all the information about a particle or a system of particles can thus be described in a wave-like manner that
is denoted mathematically by a wave function, ϕ(x, t). However, wave functions behave like waves
and can diffract, and interfere together forming superpositions, implying that quantum particles
simultaneously exist in multiple spatial locations and states. When a measurement is made, one of
the multiple states is chosen and the quantum superposition of states ends being reduced to a classical state in a process known as the collapse of the wave function.
While quantum mechanics was developed with elementary particles in mind, its subsequent
applications extended its validity to systems of many particles such as those encountered in condensed matter physics, e.g. in the description of the conduction electron ‘sea’, excitons, magnons,
polarons, polaritons, etc. These types of quantum properties of macroscopic physical systems
are called collective excitations. A system of many particles under specifc conditions cannot
be separated into individual wave functions for each particle; rather, the system is described
by a single wave function describing its collective behaviour. This physical property is called
quantum coherence, and it is characterised by individual particles losing their separate identities
so that the entire system acts as a whole. Particles that were once unifed in a common quantum
state remain physically connected even at a distance. As a consequence of the collective behaviour of many-body systems, hallmarks of quantum mechanics can be seen in the properties of
macroscopic objects such as crystals or ferromagnets, even above room temperature. There are
also more exotic direct manifestations of quantum behaviour in macroscopic systems such as
superconductors (with no measurable resistance to electrical current and ideal diamagnetism) or
superfuids (with no viscosity and infnite vorticity). However, these latter two examples have so
far been limited to very low temperatures. The precise location of the boundary (in terms of both
the object’s size and ambient temperature) between quantum and classical regimes is still under
debate.
FROM QUANTUM CHEMISTRY TO QUANTUM BIOLOGY
Extensions of quantum mechanics to chemical compounds and chemical reactions proved to be
exceedingly successful, and an entire feld of quantum chemistry was developed as a consequence.
In order to understand the creation of chemical bonds, especially covalent bonds in which electrons
are shared between atoms of a molecule, a quantum mechanical wave function was introduced into
the formalism as one of the postulates of quantum mechanics. All chemistry, including biochemistry, is based on the creation and destruction of bonds between atoms and hence on quantum interactions. Hence, by extension the structural stability of all living systems, like non-living systems,
depends on quantum states at the level of chemical bonds. However, the quantum effects are commonly claimed to be washed out due to decoherence taking place at scales larger than individual
atoms or sub-atomic particles, at higher temperatures and in aqueous media, which provide a noisy
environment for particle interactions. Thus, the likelihood of quantum states playing functional
roles at macroscopic scales in ‘warm, wet and noisy’ biological systems seems problematic due
to environmental decoherence effects. On the other hand, it is reasonable to expect that evolution,
through the process of natural selection over billions of years of experimentation and countless parallel attempts of trial and error, may have solved the decoherence problem so that quantum states
may be essential features of biological systems (Rosa and Faber, 2004).
Erwin Schrödinger, Niels Bohr, Werner Heisenberg, Eugene Wigner and their contemporaries
all offered speculations about quantum effects in living systems, while Schrödinger’s famous book
What Is Life? (Schrödinger, 1944) actually paved the way for the birth of molecular biology in the
1950s. What is still very much a mystery, however, is the perfect synchronisation of biological processes across spatial and temporal dimensions that connect the hierarchical organisational scales of
a living system. Here, quantum mechanics may indeed come to the rescue, if only we could explain
the required absence of decoherence.