# ψ-Epistemic models are exponentially bad at explaining the distinguishability of quantum states.

@article{Leifer2014EpistemicMA,
title={$\psi$-Epistemic models are exponentially bad at explaining the distinguishability of quantum states.},
author={Matthew Leifer},
journal={Physical review letters},
year={2014},
volume={112 16},
pages={
160404
}
}
• M. Leifer
• Published 30 January 2014
• Philosophy
• Physical review letters
The status of the quantum state is perhaps the most controversial issue in the foundations of quantum theory. Is it an epistemic state (state of knowledge) or an ontic state (state of reality)? In realist models of quantum theory, the epistemic view asserts that nonorthogonal quantum states correspond to overlapping probability measures over the true ontic states. This naturally accounts for a large number of otherwise puzzling quantum phenomena. For example, the indistinguishability of…
41 Citations

### Quantum superpositions cannot be epistemic

Quantum superposition states are behind many of the curious phenomena exhibited by quantum systems, including Bell non-locality, quantum interference, quantum computational speed-up, and the

### Is the quantum state real? A review of -ontology theorems

Towards the end of 2011, Pusey, Barrett and Rudolph (PBR) derived a theorem that aimed to show that the quantum state must be ontic (a state of reality) in a broad class of realist approaches to

### On the Interpretation of Quantum Indistinguishability : a No-Go Theorem

• Physics, Philosophy
• 2022
Despite being the most fundamental object in quantum theory, physicists are yet to reach a consensus on the interpretation of a quantum wavefunction. In the broad class of realist approaches, quantum

### Reality of the quantum state: Towards a stronger ψ-ontology theorem

The Pusey-Barrett-Rudolph (PBR) no-go theorem provides an argument for the reality of the quantum state by ruling out {\psi}-epistemic ontological theories, in which the quantum state is of a

### Is the Quantum State Real? An Extended Review of -ontology Theorems

The background needed for the novice in this area to understand the current status of the Pusey–Barrett–Rudolph Theorem is provided, and often overlooked subtleties should be of interest to the experts are discussed.

### Experimental test of the no-go theorem for continuous ψ-epistemic models

• Physics
Scientific reports
• 2016
This work experimentally test the no-go theorem on continuous ψ-epistemic models of quantum states with high-dimensional single photon quantum states without additional assumptions except for the fair-sampling assumption and reproduces the prediction of quantum theory.

### Bell nonlocality and the reality of the quantum wave function

• Philosophy
Physical Review A
• 2021
Status of quantum wavefunction is one of the most debated issues in quantum foundations -- whether it corresponds directly to the reality or just represents knowledge or information about some aspect

### Is a time symmetric interpretation of quantum theory possible without retrocausality?

• Philosophy
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
• 2017
It is shown that the assumption that a time symmetric ontology for quantum theory must necessarily be retrocausal can be replaced by a different assumption, called λ-mediation, that plausibly holds independently of the status of the quantum state, and that this assumption implies a timelike analogue of Bell's local causality criterion.

### Communication complexity and the reality of the wave-function

It is argued that the statement of the PBR theorem can be proved if the classical communication cost of simulating the communication of n qubits grows more than exponentially in 'n' and developed into the form of a theorem.

### Reality, causality, and quantum theory

Quantum theory describes our universe incredibly successfully. To our classically-inclined brains, however, it is a bizarre description that requires a reimagining of what fundamental reality, or

## References

SHOWING 1-10 OF 35 REFERENCES

### No ψ-epistemic model can fully explain the indistinguishability of quantum states.

• Physics
Physical review letters
• 2014
This work considers models that are defined for a single quantum system of dimension d, such that the independence condition does not arise, and derives an upper bound on the extent to which the probability distributions can overlap.

### Evidence for the epistemic view of quantum states: A toy theory

We present a toy theory that is based on a simple principle: the number of questions about the physical state of a system that are answered must always be equal to the number that are unanswered in a

### Einstein, Incompleteness, and the Epistemic View of Quantum States

• Philosophy
• 2007
It is shown that for models wherein the quantum state has the status of something real, the failure of locality can be established through an argument considerably more straightforward than Bell’s theorem.

### No-go theorems for ψ-epistemic models based on a continuity assumption.

• Philosophy
Physical review letters
• 2013
This argument is different from the recent proof of Pusey, Barrett, and Rudolph and it already yields a nontrivial constraint on ψ-epistemic models using a single copy of the system in question.

### ψ-epistemic theories: The role of symmetry

• Philosophy
• 2013
Formalizing an old desire of Einstein, “ψ-epistemic theories” try to reproduce the predictions of quantum mechanics, while viewing quantum states as ordinary probability distributions over underlying

### How statistical are quantum states

A novel no-go theorem is presented which sets a bound upon the extent to which '\Psi-epistemic' interpretations of quantum theory are able to explain the overlap between non-orthogonal quantum states

### Epistemic view of quantum states and communication complexity of quantum channels

• A. Montina
• Computer Science
Physical review letters
• 2012
It is shown that classical simulations employing a finite amount of communication can be derived from a special class of hidden variable theories where quantum states represent statistical knowledge about the classical state and not an element of reality.

### Distinct quantum states can be compatible with a single state of reality.

• Physics
Physical review letters
• 2012
This work considers models for quantum systems with measurement outcomes determined by an underlying physical state of the system but where several quantum states are consistent with a single underlying state-i.e., probability distributions for distinct quantum states overlap.

### Maximally epistemic interpretations of the quantum state and contextuality.

• Philosophy
Physical review letters
• 2013
The relationship between quantum contextuality and models of quantum theory in which the quantum state is maximally epistemic and preparation noncontextual models must be Kochen-Specker non contextual is examined to establish both the impossibility and the implication of Bell's theorem from an Einstein-Podolsky-Rosen-like argument.

### Contextuality for preparations, transformations, and unsharp measurements

The Bell-Kochen-Specker theorem establishes the impossibility of a noncontextual hidden variable model of quantum theory, or equivalently, that quantum theory is contextual. In this paper, an