REVIEW
Concentrating Partial Entanglement by Local Operations
Quantum Physics · Submitted 21 Nov 1995 · 12 references
Pith's verdict: The founding entanglement-concentration paper: the central claim is correct and has held for thirty years, with only minor exposition gaps in the standardization lemma and a couple of stray factors.
T0 · AI review
Why Pith says this
Highlight any text to comment on it.
Referee report
The paper
The paper claims
Entanglement can be concentrated: many partly entangled pairs yield nearly as many perfect singlets as their entropy allows.
The reading
What carries the argument
Schmidt projection is the central mechanism: Alice measures the total number $k$ of excited Schmidt branches across all $n$ pairs, not which pairs, projecting onto the subspace with common coefficient $��cos^{n-k}��theta��sin^k��theta$; the residual state is maximally entangled in dimension $��binom{n}{k}$. Because the distribution of $k$ has entropy $O(��log n)$, almost all of the original $nE$ entanglement survives. The standardization stage multiplies dimensions $��binom{n}{k_j}$ over batches until the product lies just above a power of two, then projects onto a $2^��ell$-dimensional subspace; local unitary rotations turn that into $��ell$ singlets. The Procrustean filter handles one pair at a time by absorbing a fraction $��tan^2��theta$ of the more probable branch.
Extended reading notes
Core claim
For any bipartite pure state $|��(A,B)��=��_i c_i|��_i��|��_i��$, the entropy of entanglement $E=-��_i c_i^2��log_2 c_i^2$ is asymptotically conserved by local operations and classical communication: $n$ copies can be converted into $nE-O(��log n)$ maximally entangled pairs, and conversely singlets can be diluted into copies of any bipartite state at the same asymptotic rate. The paper establishes this by Schmidt projection, which projects the $n$-copy state onto a subspace of fixed excitation number $k$ and leaves a maximally entangled state of dimension $��binom{n}{k}$, followed by a standardization step that groups such states until their total dimension is close to a power of two. It also gives a single-copy Procrustean method that probabilistically converts one partly entangled pair into one perfect singlet by filtering the larger Schmidt coefficient.
Load-bearing premise
The central claim depends on the unproved standardization lemma that a random walk on the unit interval with steps drawn from the binomial-coefficient distribution will, with probability one, come within a factor $1+��epsilon$ of a power of two, a lemma the paper calls elementary and states for arbitrary step distributions even though that general form fails for commensurate steps.
Original abstract
If two separated observers are supplied with entanglement, in the form of $n$ pairs of particles in identical partly-entangled pure states, one member of each pair being given to each observer; they can, by local actions of each observer, concentrate this entanglement into a smaller number of maximally-entangled pairs of particles, for example Einstein-Podolsky-Rosen singlets, similarly shared between the two observers. The concentration process asymptotically conserves {\em entropy of entanglement}---the von Neumann entropy of the partial density matrix seen by either observer---with the yield of singlets approaching, for large $n$, the base-2 entropy of entanglement of the initial partly-entangled pure state. Conversely, any pure or mixed entangled state of two systems can be produced by two classically-communicating separated observers, drawing on a supply of singlets as their sole source of entanglement.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
If two separated observers are supplied with entanglement, in the form of $n$ pairs of particles in identical partly-entangled pure states, one member of each pair being given to each observer; they can, by local actions of each observer, concentrate this entanglement into a smaller number of maximally-entangled pairs of particles, for example Einstein-Podolsky-Rosen singlets, similarly shared between the two observers. The concentration process asymptotically conserves {\em entropy of entanglement}---the von Neumann entropy of the partial density matrix seen by either observer---with the yield of singlets approaching, for large $n$, the base-2 entropy of entanglement of the initial partly-entangled pure state. Conversely, any pure or mixed entangled state of two systems can be produced by two classically-communicating separated observers, drawing on a supply of singlets as their sole source of entanglement.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | If two separated observers are supplied with entanglement, in the form of $n$ pairs of particles in identical partly-entangled pure states, one member of each pair being given to each observer; they can, by local actions of each observer, concentrate this entanglement into a smaller number of maximally-entangled pairs of particles, for example Einstein-Podolsky-Rosen singlets, similarly shared between the two observers. | contribution 0.59 | 0.60 | 0.59 | hedged possibility 0.55 |
| s1 | The concentration process asymptotically conserves {\em entropy of entanglement}---the von Neumann entropy of the partial density matrix seen by either observer---with the yield of singlets approaching, for large $n$, the base-2 entropy of entanglement of the initial partly-entangled pure state. | result 0.99 | 0.80 | 0.40 | asserted 0.99 |
| s2 | Conversely, any pure or mixed entangled state of two systems can be produced by two classically-communicating separated observers, drawing on a supply of singlets as their sole source of entanglement. | result 0.83 | 0.44 | 0.19 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v1
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
References
How later papers used it
362 later papers cite it
4 later papers by other authors are listed below: 1 built on it and 3 used its method or tool.
Builds on it 1 of 4 papers with this label
-
Generalized this paper's Tiles UPB in $ℂ^3⊗ℂ^3$ in its construction.
Family of bound entangled states on the boundary of Peres set (2018) · 1.00 · paraphrased: the licence does not allow quoting
Uses its method or tool 3 of 16 papers with this label
-
Adopted the so-called Procrustean method of filtering from this paper, following the approach in another work.
Loss-tolerant quantum key distribution with detection efficiency mismatch (2024) · 1.00 · paraphrased: the licence does not allow quoting
-
Used entanglement and LOCC as related to this paper's approach to form approximate copies of a bosonic Gaussian resource state.
Entanglement cost and quantum channel simulation (2018) · 0.96 · paraphrased: the licence does not allow quoting
-
We measure the degree of entanglement between the two species by computing the von Neumann entanglement entropy [ref] using the reduced density matrices $ρ_2=Tr_1(ρ)$ or $ρ_1=Tr_2(ρ)$
Entangled Collective Spin States of Two Species Ultracold atoms in a Ring (2023) · States and Entanglement Entropy · 0.94
How the literature uses it
68 arXiv papers cite this in 79 sentences
Papers whose main result relates to this one's
States the same result 1 paper
-
If two parties, Alice and Bob, share some number, n, of partially entangled pairs of qubits, then it is possible for them to concentrate these pairs into some smaller number of maximally entangled states.
Papers citing it · 38 sentences without a confident label
Builds on it 1 paper
-
Now let us consider an interpretation of pseudo entropy from the view point of quantum entanglement by extending the well-known argument [ref] for the entanglement entropy.
Holographic Pseudo Entropy · Interpretation via Quantum Entanglement · 0.99
Uses its method or tool 2 papers
-
Now, the idea of forming $n$ approximate copies $ψ_A^'B^' ^ω$ is then the same as it is in [ref] : Alice prepares the state $ψ_A^'nB^'n^ω$ locally, Alice and Bob require beforehand a maximally entangled state of Schmidt rank no larger than $2^n[ H(B^')_ψ^ω+δ]$, and then they perform quantum teleportation [ref] to teleport the $B^'n$ system to Bob.
Entanglement cost and quantum channel simulation · Upper bound on the entanglement cost of teleportation-simulable channels with bosonic Gaussian resource states · 0.91
-
The entanglement entropy $S_EE(r)$, determined by the Von Neumann entropy on the reduced density matrix of one of the subsystems, is defined by [ref] [equation] The required $2×2$ reduced density matrix of the state $|ψ_e(r)⟩$ can be expressed as [equation] where $λ_1(r)$ and $λ_2(r)$ are the two nonzero eigenvalues of $ρ_e(r)$.
Probing the quantum speed limit and entanglement in flavor oscillations of neutrino-antineutrino system in curved spacetime · Entanglement in two-flavor oscillations of the neutrino-antineutrino system in curved spacetime · 0.90
Compares with it 1 paper
-
Now, in known dilution protocols, the amount of entanglement does not fluctuate, while the original entanglement concentration [ref] protocol, is one where the final amount of entanglement does fluctuate, but probabilistically rather than coherently.
Entanglement fluctuation theorems · Probabilistic BLOCC transformations and full reversibility of entanglement dilution and concentration · 0.91
Cites it as background 35 papers
-
The central result on transformations between bipartite pure states with asymptotically vanishing error is that the optimal rate is the ratio of the (von Neumann) entropies of entanglement of the two states [ref] .
Error exponents for tripartite-to-bipartite entanglement transformations · Introduction · 0.89
-
Entanglement distillation protocols [ref] in quantum information theory allow the extraction of maximally entangled Bell states from multiple copies of weakly entangled or noisy states.
Nonlocality distillation can outperform entanglement distillation · Introduction · 0.98
-
In this chapter, we focus on two different information-processing tasks relevant for bipartite quantum interactions, the first being entanglement distillation [ref] and the second secret key agreement [ref] .
Bipartite Quantum Interactions: Entangling and Information Processing Abilities · Entropy of Entanglement · 0.93
Discussion
Disagree with the review, or know something it missed? Leave a comment, highlight any passage above to comment on it, or challenge this review formally.