Terms starting with Q
17 terms
Q-Value
Nuclear & Particle Physics
MeV (Mega-electronvolts)
The net amount of energy released or absorbed during a nuclear reaction or radioactive decay process.
Q = (m_reactants - m_products) c²
Quantum Chromodynamics (QCD)
Nuclear & Particle Physics
Non-Abelian Gauge Theory
The relativistic quantum field theory describing the strong nuclear interaction between color-charged quarks and gluons.
L_QCD = q̄ (i γ^μ D_μ - m) q - ¼ G^a_μν G^a,μν
Quantum Confinement Effect
Condensed Matter & Materials Physics
eV (Confinement Energy Shift)
The shift and quantization of electronic energy levels when charge carriers are confined within spatial dimensions smaller than their De Broglie wavelength.
E_confinement ∝ 1 / L² (When dimension L ≤ De Broglie wavelength)
Quantum Decoherence
Quantum & Atomic Physics
s (Decoherence Time Constant)
The loss of quantum coherence where interaction between a quantum system and its macro-environment converts a quantum superposition into a classical probabilistic mixture.
ρ_offdiag(t) = ρ_offdiag(0) e^(-t / τ_dec)
Quantum Dots
Quantum & Atomic Physics
nm (Size), eV (Bandgap)
Nanometer-scale semiconductor crystals that trap charge carriers in all three spatial dimensions, exhibiting artificial atom quantized energy spectra.
E_gap(R) = E_bulk + (ℏ² π²) / (2 m_eff R²)
Quantum Electrodynamics (QED)
Quantum & Atomic Physics
Relativistic Quantum Field
The relativistic quantum field theory describing how light (photons) and charged matter (electrons/positrons) interact.
L_QED = ψ̄ (i γ^μ D_μ - m) ψ - ¼ F_μν F^μν
Quantum Entanglement
Quantum & Atomic Physics
Dimensionless Quantum State
A quantum phenomenon in which two or more particles become interconnected such that the quantum state of each particle cannot be described independently of the others.
|Ψ⟩ = (1 / √2) (|0⟩|1⟩ - |1⟩|0⟩)
Quantum Hall Effect
Condensed Matter & Materials Physics
Ω (Von Klitzing Constant R_K ≈ 25812.807 Ω)
A quantum mechanical version of the Hall effect observed in 2D electron gases at low temperatures and intense magnetic fields, where Hall resistance is quantized in integer multiples of h/e².
R_H = h / (ν e²), ν = 1, 2, 3...
Quantum Harmonic Oscillator
Quantum & Atomic Physics
eV or Joules
The quantum mechanical analogue of a classical harmonic oscillator, describing a particle bound in a parabolic potential well V(x) = ½ m ω² x².
E_n = (n + ½) ℏ ω, n = 0, 1, 2, 3...
Quantum Operators
Quantum & Atomic Physics
Varies by Observable
Linear mathematical operators that act on a wave function to yield physical observables (such as position, momentum, or energy).
p̂ = -i ℏ ∇, x̂ = x, Ĥ = -(ℏ² / (2m)) ∇² + V(x)
Quantum Superposition
Quantum & Atomic Physics
Dimensionless State Vector
A core principle of quantum mechanics stating that a quantum system can exist in a linear combination of multiple distinct quantum states simultaneously until measured.
|Ψ⟩ = α |0⟩ + β |1⟩, |α|² + |β|² = 1
Quantum Tunneling
Quantum & Atomic Physics
Dimensionless (Transmission Probability)
A quantum phenomenon where a particle passes through a potential energy barrier higher than the particle's kinetic energy.
T ≈ exp(-2 k L), k = √(2 m (V₀ - E)) / ℏ
Quark Flavor
Nuclear & Particle Physics
Quantum Numbers (S, C, B, T)
The quantum property that distinguishes the six fundamental types of quarks in the Standard Model.
6 Flavors: u, d, c, s, t, b
Quark-Gluon Plasma (QGP)
Plasma Physics
MeV (Transition Temperature)
A extreme phase of quantum chromodynamic (QCD) matter where hadrons melt into a deconfined state of free quarks and gluons at extreme temperatures.
T_deconfinement ≈ 150–170 MeV (~2 × 10¹² K)
Quarks
Nuclear & Particle Physics
Fractional Elementary Charge e
Fundamental spin-1/2 elementary particles that experience all four fundamental interactions and combine via the strong force to form hadrons.
q = +⅔ e (u, c, t), q = -⅓ e (d, s, b)
Quasar
Astrophysics, Cosmology & Relativity
Luminosity / Redshift z
An extremely luminous Active Galactic Nucleus (AGN) powered by gas accreting onto a supermassive black hole at the center of a distant galaxy.
L_quasar ~ 10⁴⁰ W (100–1000 times Milky Way Luminosity)
Quasi-neutrality
Plasma Physics
Dimensionless Balance Condition
The property of a plasma where positive ion charge density and negative electron charge density are nearly equal across spatial scales larger than the Debye length.
n_e ≈ ∑ Z_i n_i (For scale lengths L ≫ λ_D)