Quantum Dictionary

A

  • Amplitude
    How tall a wave is. Bigger amplitude means a taller wave and more energy—like higher peaks on the ocean!
  • Atom
    A tiny building-block of matter (or stuff). Atoms are made up of small particles stuck together in different ways.

B

  • Bit
    A tiny piece of information that can be 0 or 1. Computers today use trillions of them every second.

C

  • Coherence
    When waves line up just right so that they interfere in a nice even way, we call it coherence. Coherent waves can make new waves which are double the size, or with no size it all!
  • Collapse
    Collapse happens after we do our measurement. If we measure a particle in a superposition, it stops being in a superposition and stays just how we measured it!
  • Continuous
    Continuous things go up and down smoothly - not one by one. Imagine the stairs got closer and closer together, until there were so many it would be impossible to count, then they become continuous.

D

  • Discrete
    Discrete things go up and down one by one, like stairs, or the numbers we count with.

E

  • Energy
    Waves are caused by energy moving through things. A wave in the ocean is energy moving through water and the sounds we hear are energy moving through air. In the quantum world, particles can also behave like waves.
  • Entanglement
    Entanglement is what we call it when two things have some joint properties (like energy or spin). When things are entangled, we can learn something about one by measuring the other, even if they are very for away! Entanglement can be used to do lots of interesting things, like making faster computers or safer communication!

F

  • Force
    Forces make energy move from one thing to another. Pushing something is applying a force to it - this gives it energy and makes it move!

I

  • Interference
    Sometimes waves can join together to make different waves - we call this interference. The new waves they make can have different shape and size!

M

  • Measurement
    Measurement this is when we look at something to learn something about it. It could be to check where it is, how fast it's going, or even how it's spinning.

N

  • Noise
    Disturbances—heat, radio waves, vibrations—that change the states of qubits in unwanted ways.

O

  • Observable
    A quantum property we can measure—like position, spin, or energy. Each has its own set of possible outcomes.

P

  • Particle
    A particle is a very tiny piece of stuff, which sticks together with other particles to make all the bigger stuff around us. Imagine dust or sand - but much, much smaller.
  • Photon
    A quantum of light—both a wave and a particle—flying along at light-speed.
  • Probability
    Probability tells us how likely something is to happen. When we toss a coin, half the time it lands heads and half the time it lands tails, so we say they have the same probability.

Q

  • Quanta
    Quanta are very small amounts of things. But they don't have to be like particles, they can be very small amounts of things like energy. A quantum of energy is like a very small packet of energy. Quanta are discrete.
  • Quantum circuit
    A quantum circuit is a whole load of quantum gates which changes the states of lots of qubits. The right set of instructions can create a quantum algorithm to make a calculation – or mimic the behaviour of another quantum system.
  • Quantum Computer
    A machine that connects lots of qubits together, using superposition and entanglement to solve certain problems faster than any classical computer.
  • Quantum gate
    A tiny operation, or instruction, that changes the state of qubit. This could be flipping the direction of its spin or, creating entanglement with other qubits.
  • Quantum information
    Knowledge stored in qubits, where we give meaning to their different quantum states.
  • Qubit
    A quantum particle which has two different states. These could be 2 amounts of energy, or two directions of spin! A qubit can be in each of the two states – or a superposition of both.

S

  • Spin
    Spin is something particles do which is a bit like spinning around in circles. All particles spin, but a different speeds and in different directions! Spin is a quantum property - so it comes in small, discrete amounts.
  • State
    The complete description of a quantum system (like particle). The state tells us as much as we can know about what the particle is doing (how it is spinning, or how much energy it has).
  • Superposition
    Superposition is what we call it when we don't know for sure where a particle is, how fast its moving or how it is spinning - but we know all the probabilities. Sometimes we just can't know any more until we check.

T

  • Tunneling
    Since particles can behave like waves, sometimes they can tunnel through barriers which should be to big for them. There's always a small probability for tunneling.

W

  • Wave
    Energy is what makes things move, change, get hot and do work. Everything that happens in the world needs energy - and it never disappears, it just moves around and changes! Energy makes particles jiggle about and bump into each other, this is how they share energy!
  • Wave packet
    A wave packet is a group of waves which move together. They are caused by lots of waves interfering with each other.
  • Wavefunction
    A fancy word we use to mean the state of a quantum system.

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