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Cat state

In quantum mechanics, the cat state, named after Schrödinger's cat, refers to a quantum state.

Version
v1 · 2026-09-28 · History
Domain-specific #
8358
Domain group
Natural Sciences
Origin domain
Physics
Subdomains
Quantum Mechanics, Quantum Optics → Physics

Core Idea

Cat state is treated here as the recurring mathematicslogicstatistics identity summarized by this source-grounded definition: In quantum mechanics, the cat state, named after Schrödinger's cat, refers to a quantum state. In quantum mechanics, the cat state, named after Schrödinger's cat, refers to a quantum state. Generalizing Erwin Schrödinger's thought experiment, a cat state is a quantum superposition of two macroscopically distinct states. A cat state could be of one or more modes or particles, yet not necessarily an entangled state. Such cat states have been experimentally realized in various ways and at various scales.

How would you explain it like I'm…

 

No faithful explanation at this level. All three agree any five-year-old picture collapses the superposition into either hidden ignorance (secretly alive or dead) or two ordinary things/halves at once, both of which the concept rules out.

The Two-Way Quantum Blend

In the world of the very tiny, physicists describe things with 'quantum states', and a quantum state can be a special combination of two different possibilities at once, called a superposition. It is not that the thing secretly is one way and we just don't know which, and it is not a half-and-half blend either; it is a new kind of state with no everyday match. A cat state is a superposition of two possibilities that are very different from each other on a big scale, like two clearly separate positions. It is named after a famous thought experiment about a cat by the scientist Erwin Schrödinger. Scientists have actually made cat states, often using light, and they are interesting for building quantum computers.

Macroscopic Superposition State

A cat state, named after Schrödinger's cat thought experiment, is a quantum superposition of two macroscopically distinct states. In a superposition the two possibilities combine with definite relative phases and can interfere, which is what separates it from a simple mixture where the system is just one or the other and we are ignorant which. The two parts of a cat state are far apart in some big-scale sense, not merely two nearby microscopic options. A cat state can live in one mode or particle or in several, and it need not be entangled. The most common realization is a superposition of two coherent states of a single optical mode of light, and such states matter for quantum computing.

 

In quantum mechanics a cat state is a coherent superposition of two macroscopically distinct states, generalizing Schrödinger's cat thought experiment. Coherence is the key: the state is a single vector with a well-defined relative phase between its two components, so interference is possible, unlike a classical probabilistic mixture. The components must differ in a macroscopic or strongly distinguishable way, such as two coherent states of light with widely separated amplitudes. The definition does not require multiple particles or entanglement; a cat state can be of a single mode. Cat states have been produced experimentally in several systems and at various scales, with the two-coherent-state superposition of one optical mode being the standard example. They are of special interest for quantum computing.

Scope of Application

  • Linear superposition of coherent states. A method to generate a larger cat state using homodyne conditioning on a number state split by a beam splitter was suggested and experimentally demonstrated with a clear separation between the.

  • Over distinct particles. Since GHZ states are relatively difficult to produce but easy to verify they are often used as a benchmark for different platforms.

  • Linear superposition of coherent states. This method usually is restricted to small values of \alpha , and such states have been referred to as Schrödinger "kitten" states in the literature.

  • Linear superposition of coherent states. More methods have been proposed to produce larger coherent state superpositions through multiphoton subtraction, through ancilla-assisted subtraction, or through multiple photon catalysis steps.

  • Linear superposition of coherent states. Optical methods to "breed" cat states by entangling two smaller "kitten" states on a beamsplitter and performing a homodyne measurement on one output have also been proposed and experimentally demonstrated.

Clarity

A clear use of Cat state names the carrier, the operative relation, and the conditions under which the source treats the identity as present. The minimal definition is In quantum mechanics, the cat state, named after Schrödinger's cat, refers to a quantum state. The strongest recognition evidence in the frozen account is: Even and odd coherent states were first introduced by Dodonov, Malkin, and Man'ko in 1974.

Manages Complexity

Cat state compresses multiple mathematicslogicstatistics details into a stable diagnostic relation. The source shows both the central mechanism—these have been experimentally realized by a team led by Pan Jianwei at University of Science and Technology of China, for instance, four-photon entanglement, five-photon entanglement, six-photon entanglement, eight-photon entanglement, and five-photon ten-qubit cat state.—and the practical consequence—a method to generate a larger cat state using homodyne conditioning on a.

Abstract Reasoning

  1. Type the carrier. Identify the mathematicslogicstatistics entities to which the claim applies.
  2. State the relation. Use the source-grounded identity: In quantum mechanics, the cat state, named after Schrödinger's cat, refers to a quantum state.
  3. Check operation and conditions. This spin up/down formulation was proposed by David Bohm, who conceived of spin as an observable in a version of thought experiments formulated in the 1935 EPR paradox.
  4. Demand recognition evidence.

Knowledge Transfer

Within the home domain. Knowledge about Cat state transfers literally when a new case preserves the same carrier type, relation, and recognition test. A method to generate a larger cat state using homodyne conditioning on a number state split by a beam splitter was suggested and experimentally demonstrated with a clear separation between the two Gaussian peaks in the Wigner function. Since GHZ states are.

Relationships to Other Abstractions

Local relationship map for Cat stateParents appear above the current abstraction, mutual partners to the right, and children below. Node labels state whether each abstraction is prime or domain-specific; colors identify relation types.Cat stateDOMAINDomain-specific abstraction: Quantum State — is a kind ofQuantum StateDOMAIN

Current abstraction Cat state Domain-specific

Parents (1) — more general patterns this builds on

  • Cat state is a kind of Quantum State Domain-specific

    A cat state is a quantum superposition state with macroscopically distinct or coherent components.

Hierarchy path (1) — routes to 1 parentless root

Neighborhood in Abstraction Space

Cat state sits in a sparse region of the domain-specific corpus (62nd percentile for distinctiveness): few abstractions share its structure, so a faithful description tends to retrieve it precisely.

Family — Quantum States & Information Measures (25 abstractions)

Nearest neighbors

Computed from structural-signature embeddings · 2026-10-08