Quantum Superposition Calculator
Calculate quantum superposition states, interference effects, coherence, and phase relationships.
About this calculator
This calculator models a simple two-state quantum superposition, |psi> = alpha|0> + beta * e^(i*phi) |1>, the building block behind qubits and interference experiments. State 1 Amplitude and State 2 Amplitude are entered as raw values and immediately normalized (each divided by the combined amplitudes' Euclidean norm) so the resulting state satisfies the physical requirement that total probability sums to 1 -- entering unequal or even unnormalized amplitudes is fine, since the calculator does the normalizing for you. State 1 Probability and State 2 Probability are simply the squared normalized amplitudes (the Born rule), showing the odds of measuring the system in each basis state.
Phase Difference controls how the two components interfere when combined: the Interference Term (2 x normalized1 x normalized2 x cos(phase)) is at its positive maximum when Phase Difference is 0 (constructive interference) and at its negative minimum when Phase Difference is pi (destructive interference), the same cosine relationship that governs fringe patterns in a double-slit or Mach-Zehnder interferometer. Visibility, the standard optical-interference figure of merit (2 x normalized1 x normalized2 over the sum of their squares), reports how strong that interference contrast is on a 0-1 scale -- 1 means perfect fringe contrast, achieved only when the two amplitudes are exactly equal. Coherence (the absolute product of the two normalized amplitudes) and the equal Superposition Quality measure how genuinely "quantum" the superposition is: both collapse toward 0 if either state's amplitude collapses toward 0, which is exactly what happens physically as decoherence pushes a system toward a definite classical state.
Inputs
Results
State 1 Probability
50%
State 2 Probability
50%
Superposition Magnitude
1.414
Interference Term
1
How to Use This Calculator
- Enter State 1 Amplitude and State 2 Amplitude (each 0–1). Unequal or unnormalized values are fine — the calculator normalizes them for you so the resulting state satisfies α₁² + α₂² = 1.
- Set Phase Difference (rad): 0 gives constructive interference, π gives destructive interference.
- Read Interference Term to see how the phase relationship amplifies or cancels the combined wavefunction.
- Visibility (0–1) indicates how strong the interference pattern is — 1 is perfect contrast, 0 is no fringe.
- Coherence (0–1) measures how quantum the superposition is; values near 0 indicate decoherence has occurred.
How the result changes with State 1 Amplitude
| State 1 Amplitude | State 1 Probability | State 2 Probability | Superposition Magnitude |
|---|---|---|---|
| 0.35 | 19.95% | 80.05% | 1.341 |
| 0.53 | 35.98% | 64.02% | 1.4 |
| 1 | 66.67% | 33.33% | 1.394 |
What each input means
- State 1 Amplitude
- Amplitude for first state
- State 2 Amplitude
- Amplitude for second state
- Phase Difference
- Phase difference between states
How this is calculated
Formula
|ψ⟩ = α|0⟩ + βe^(iφ)|1⟩Worked example, using the default values
- Identify Input ParametersState 1 Amplitude = 0.707, State 2 Amplitude = 0.707, Phase Difference = 0 = 3 input(s) provided
- Calculate State 1 ProbabilityState 1 Probability50 = 50%
- Calculate State 2 ProbabilityState 2 Probability50 = 50%
- Calculate Superposition MagnitudeSuperposition Magnitude1.414 = 1.414
- Calculate CoherenceCoherence0.5 = 0.5
- Calculate VisibilityVisibility1 = 1
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why do I need to enter amplitudes instead of probabilities directly?
Quantum states are described by complex probability amplitudes, not probabilities themselves, because amplitudes can interfere -- add constructively or destructively -- in a way plain probabilities cannot. The calculator squares the normalized amplitudes to give you State 1 Probability and State 2 Probability, but it needs the amplitudes first to correctly compute the Interference Term and Visibility, which depend on the amplitudes' relative phase, not just their magnitudes.
Why does changing Phase Difference not affect State 1 Probability or State 2 Probability?
State 1 Probability and State 2 Probability come from squaring the normalized amplitudes alone -- the phase term only enters once the two components are combined into the full superposition state, which is what the Interference Term, Superposition Magnitude, Visibility, and Phase Sensitivity outputs capture. The individual-state probabilities describe what you'd measure in the computational basis, where relative phase has no effect.
What does a Visibility of 1 versus 0 actually mean?
Visibility of 1 means the two amplitude components have exactly equal magnitude, producing maximum interference contrast -- the Interference Term swings through its full possible range as Phase Difference varies. Visibility of 0 means one amplitude has collapsed to zero, so there's effectively only one state left and no interference pattern to speak of, since interference requires two non-zero components to combine.
How is Coherence different from the individual state probabilities?
State 1 Probability and State 2 Probability each describe one component in isolation, while Coherence (the absolute product of both normalized amplitudes) specifically measures the cross-term that only exists because the system is in a genuine superposition rather than a classical mixture. Coherence is highest when both amplitudes are equal and falls toward zero as either one dominates, tracking how much quantum interference the state can actually exhibit.
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