Blog of Veikko M.O.T. Nyfors, Hybrid Quantum ICT consultant

Quantum Mechanics demystified, a try

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Quantum objects and properties

Quantum objects obey rules of quantum mechanics. Most notably their properties are not continuous but quantized. Quantization happens in Planck’s scale, i.e. in very, very small bundles. Plancs constant h=6.62607015 × 10^-34, describes the scale.
Actually, it is that the quantization is distinquishable only in Planck’s scale objects. For larger objects things get somehow averaged to follow the rules of classical Newtonian physics. We just don’t quite understand it yet why this is as it is. Or maybe I just am not aware of it.

Photons, electrons, atoms and even molecules up to certain size are typical samples of quantum objects, per current understanding.
Quantum object may have various measurable quantum properties, degrees of freedom, like position, momentum, angular momentum, energy and spin. Below a couple of samples.

• Photon
  • polarization ~ spin
  • x-y-z location
  • time
• Electron - quantum numbers are associated with electrons position around nucleus
  • Principal quantum number, $n$. Energy level or shell/orbital electron is in an atom.
  • Azimuthal quantum number, $l$. Orbital angular momentum, shape of the orbital, a.k.a. sub-shell. Values 0 - $n$-1.
  • Magnetic quantum number, $m_l$. Values $-l\hspace{1em} to \hspace{1em} +l$, including 0.
  • Spin, $s$. Values $+1/2 \hspace{1em} -1/2$
  • Being a fermion, i.e. obeying Pauli exclusion rules, $n, l, m_l$ and $s$ provide unique quantum states for electrons on orbitals.
    • Allowing 2 electrons on first $n=1$ shell, with distinct spin.
    • 8 electrons on $n=2$, with $l=0,1$, $m_l=-1,0,+1$ and $s=+1/2, -1/2$
    • 18 on $n=3$
    • etc