A subtraction event weights initial occupation $n$ by $n$ before removing one photon. Thus its conditional output mean is $⟨N(N-1)⟩/\mu$, giving the displayed identity for $\mu >0$. If the initial variance exceeds its mean, this biased selection can offset the removed photon. The unconditional ensemble includes unsuccessful events and has a different energy balance.

Raw vectors $a^{†}|\psi ⟩$ and $a|\psi ⟩$ have squared norms $\mu +1$ and $\mu$. Matrix elements of the number operator in these vectors must be divided by their squared norms before calling them means. For an optical squeezed vacuum with mean $s$, the raw moments are $(3s+1)(s+1)$ and $s(3s+1)$, while both normalized means equal $3s+1$ when subtraction is possible.

Sub-Poissonian number variance in a specified mode or detection gate. It concerns photon counting, not an optical quadrature. An optical squeezed vacuum has quadrature squeezing but fails this number-variance condition.

A monochromatic beam of frequency $f$ and mean radiated power $P$ carries mean photon rate $\dot{N}=P/(hf)$. It follows by dividing energy per unit time by energy per photon. A broadband source instead requires integrating spectral power divided by the frequency-dependent photon energy; electrical input power must first be converted to radiated power.

Count detections in two channels within a specified time window to estimate pair correlations. Delayed windows or independent singles rates estimate accidental coincidences. Finite efficiency, timing jitter, dark counts and multiple pairs must be included before interpreting a coincidence fringe as a property of the prepared state.

The effective area per target for absorbing incident radiation at a specified wavelength. For independent absorbers with number column $N$, the absorption optical depth is $\tau ={\sigma }_{\mathrm{abs}}N$. Absorption does not guarantee a particular chemical product; a channel's quantum yield is also needed in its photolysis rate coefficient.

A measured emission intensity as excitation photon energy is varied, with emitted energy also selected or resolved. Excitation-emission maps can separate transitions belonging to different semiconducting carbon nanotubes.

Two or more photons detected within one unresolved spatial and temporal event cell can be registered as one event, have their energies combined, or be rejected by event grading. In an X-ray CCD, low mean occupancy per event island per frame is needed for reliable individual-photon spectroscopy. Reducing frame time or spreading the image can reduce this effect.

The glucose-specific enzyme-IIA component of the bacterial phosphotransferase system. Its dephosphorylated form can bind lactose permease, causing inducer exclusion.

phosphatidylinositol 3,4-bisphosphate has phosphates at positions 3 and 4 of the inositol ring. Local production can contribute to timed recruitment of endocytic membrane-remodeling factors.

phosphatidylinositol 3-phosphate is a phosphoinositide associated with endosomal membrane identity and recruitment of specific effectors.

phosphatidylinositol 3,5-bisphosphate is a doubly phosphorylated phosphoinositide involved in later endolysosomal organization and function. Perturbing it need not imply that initial surface uptake is defective.

A phosphoinositide enriched in particular membrane domains, including Golgi-associated compartments.

vitrification produces a noncrystalline glassy state. Rapid freezing of thin aqueous specimens is used to preserve hydrated biological structures for cryo-electron microscopy; vitrification does not prevent all subsequent radiation damage.

A cooperative change of atomic positions and lattice shape without the long-range compositional diffusion required by a diffusional transformation. Tetragonal-to-monoclinic transformation in zirconia is a nonmetallic example.

A two-dimensional phase with quasi-long-range sixfold bond-orientational order but short-range translational order. A cell model of independent particle cages does not capture its full physics.

A structural phase change requiring substantial rearrangement of near-neighbor bonding or connectivity. Its activation barriers can make equilibrium transitions kinetically sluggish. It is distinguished from a cooperative displacive transformation, rather than defined solely by the presence of a different final symmetry.

Formation of a crystal from a disordered phase. In a cooling white dwarf, crystallization of the ionic interior releases latent heat and can redistribute chemical species, affecting the relation between luminosity and white-dwarf cooling age.