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Terms starting with Q

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Nuclear & Particle Physics

Q-Value

The net amount of energy released or absorbed during a nuclear reaction or radioactive decay process.

Q = (m_reactants - m_products) c² MeV (Mega-electronvolts)
Nuclear & Particle Physics

Quantum Chromodynamics (QCD)

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 Non-Abelian Gauge Theory
Condensed Matter & Materials Physics

Quantum Confinement Effect

The shift and quantization of electronic energy levels when charge carriers are confined within spatial dimensions smaller than their De…

E_confinement ∝ 1 / L² (When dimension L ≤ De Broglie wavelength) eV (Confinement Energy Shift)
Quantum & Atomic Physics

Quantum Decoherence

The loss of quantum coherence where interaction between a quantum system and its macro-environment converts a quantum superposition into a…

ρ_offdiag(t) = ρ_offdiag(0) e^(-t / τ_dec) s (Decoherence Time Constant)
Quantum & Atomic Physics

Quantum Dots

Nanometer-scale semiconductor crystals that trap charge carriers in all three spatial dimensions, exhibiting artificial atom quantized…

E_gap(R) = E_bulk + (ℏ² π²) / (2 m_eff R²) nm (Size), eV (Bandgap)
Quantum & Atomic Physics

Quantum Electrodynamics (QED)

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 Relativistic Quantum Field
Quantum & Atomic Physics

Quantum Entanglement

A quantum phenomenon in which two or more particles become interconnected such that the quantum state of each particle cannot be described…

|Ψ⟩ = (1 / √2) (|0⟩|1⟩ - |1⟩|0⟩) Dimensionless Quantum State
Condensed Matter & Materials Physics

Quantum Hall Effect

A quantum mechanical version of the Hall effect observed in 2D electron gases at low temperatures and intense magnetic fields, where Hall…

R_H = h / (ν e²), ν = 1, 2, 3... Ω (Von Klitzing Constant R_K ≈ 25812.807 Ω)
Quantum & Atomic Physics

Quantum Harmonic Oscillator

The quantum mechanical analogue of a classical harmonic oscillator, describing a particle bound in a parabolic potential well V(x) = ½ m ω²…

E_n = (n + ½) ℏ ω, n = 0, 1, 2, 3... eV or Joules
Quantum & Atomic Physics

Quantum Operators

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) Varies by Observable
Quantum & Atomic Physics

Quantum Superposition

A core principle of quantum mechanics stating that a quantum system can exist in a linear combination of multiple distinct quantum states…

|Ψ⟩ = α |0⟩ + β |1⟩, |α|² + |β|² = 1 Dimensionless State Vector
Quantum & Atomic Physics

Quantum Tunneling

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 Dimensionless (Transmission Probability)
Nuclear & Particle Physics

Quark Flavor

The quantum property that distinguishes the six fundamental types of quarks in the Standard Model.

6 Flavors: u, d, c, s, t, b Quantum Numbers (S, C, B, T)
Plasma Physics

Quark-Gluon Plasma (QGP)

A extreme phase of quantum chromodynamic (QCD) matter where hadrons melt into a deconfined state of free quarks and gluons at extreme…

T_deconfinement ≈ 150–170 MeV (~2 × 10¹² K) MeV (Transition Temperature)
Nuclear & Particle Physics

Quarks

Fundamental spin-1/2 elementary particles that experience all four fundamental interactions and combine via the strong force to form…

q = +⅔ e (u, c, t), q = -⅓ e (d, s, b) Fractional Elementary Charge e
Astrophysics, Cosmology & Relativity

Quasar

An extremely luminous Active Galactic Nucleus (AGN) powered by gas accreting onto a supermassive black hole at the center of a distant…

L_quasar ~ 10⁴⁰ W (100–1000 times Milky Way Luminosity) Luminosity / Redshift z
Plasma Physics

Quasi-neutrality

The property of a plasma where positive ion charge density and negative electron charge density are nearly equal across spatial scales…

n_e ≈ ∑ Z_i n_i (For scale lengths L ≫ λ_D) Dimensionless Balance Condition