The Birth of Quantum Biology

Roland Piquepaille writes "Just when you finally have grasped the concept of quantum mechanics, it's time to wake up and to see the arrival of a nascent field named quantum biology. This is the scientific study of biological processes in terms of quantum mechanics and it uses today's high-performance computers to precisely model these processes. And this is what researchers at Rensselaer Polytechnic Institute (RPI) are doing, using powerful computer models to reveal biological mechanisms. Right now, they're working on a "nanoswitch" that might be used for a variety of applications, such as targeted drug delivery to sensors."

Comments

Re:How is this any different?

[wass]

Well, physics is much more than freshman ballistics problems, but you're correct in that the complexity becomes significantly more difficult. Eg, in elementary quantum mechanics one can build a 'Hamiltonian' for any system, and usually you approximate things such as excluding the Coulomb force between every set of electrons, and that neutrons, electrons, and protons act as tiny magnets so they interact that way, and that there are spin-relational effcts, etc. Each of these adds terms to the Hamiltonian, but usually there's a convergence as the correction terms are smaller and smaller and can be neglected. Actually, that's why QED is so easy but QCD gets harder, because secondary and higher interactions in QED have decreasing significance but no so much in QCD where things diverge.

So in some sense you know the basic 'laws' of the universe, and right now we have pretty reasonable understanding of most things, neglecting large scales (dark matter, dark energy) and large energies (Higgs boson, gravitons, etc). But for stuff within our local spheres of observation, we have basic laws that account for most things we can see, so we should theoretically be able to model anything in this frame. The problem is that it becomes super complex very quickly.

Okay, so why there are so few solvable problems is mathematical. Eg, in the hydrogen atom, we can easily solve the differential equation that comes from the Schrodinger equation. Ie, you write the kinetic energy as T=p^2/2m, you write the potential energy as U=-e^2/r, giving a total energy of E=p^2/2m - e^2/r. You should recognize this as the standard kinetic energy written using momentum instead of velocity, and the Coulomb potential energy between the electron and proton. The system is an electron orbiting a proton, and in the center-of-mass units r is the distance between the two, and m is the reduced mass, which is fairly close to the electron. This is all well and good, and when put into the realm of quantum mechanics, r and p go from being canonical coordinates to being canonical operators. When put into the position basis, the p operator acts as a derivative of the r coordinate, and this yields a differential equation that must be solved to give the eigenstates of the solution. The system is spherically-symmetric which makes things much easier, and after solving the three-dimensional 2nd-order differential equations you get the solutions of atomic orbitals that you probably studied about in high-school chemistry class.

Now this is the 'simple' system. When you start adding relativistic corrections to that kinetic energy and when you add the interaction of the electron's magnetic moment interacting with the magnetic field creating as it orbits the proton, this yields the fine structure. You can also add in the spin-spin interaction between the magnetic moment of the electron and the proton, which gives the hyperfine interaction. Each of these things makes the differential equations MUCH harder to solve, and at some point we just don't mathematically know how to solve these complex systems of equations. Helium atom gets much harder because there are now two position coordinates of each atom, and an extra Coulomb interaction term. This is a quantum three-body problem, and even in classical mechanics the three-body problem cannot be solved in general. Ie, there is no KNOWN exact solution for any three bodies.

Anyway, you can see where this is going. But while we cannot know exact solutions, we can approximate them numerically to arbitrarily-small precision (at least with classical mechanics where there is no uncertainty principle). This is where the shiny computers come in. We can model easily how 10 bodies orbit around the sun AND interact with each other, but to get a general algebraic solution of them for any point in time, we cannot do.