The DOI matches its Crossref record; 8 of the 22 references it cites were found in a registry or an index, and 14 are not checked yet; none of the 4 sources its claims cite is checked for support yet.
Perfect State Transfer in Quantum Spin Networks
Open accessAbstract
We propose a class of qubit networks that admit the perfect state transfer of any quantum state in a fixed period of time. Unlike many other schemes for quantum computation and communication, these networks do not require qubit couplings to be switched on and off. When restricted to N-qubit spin networks of identical qubit couplings, we show that 2log3N is the maximal perfect communication distance for hypercube geometries. Moreover, if one allows fixed but different couplings between the qubits, then perfect state transfer can be achieved over arbitrarily long distances in a linear chain.
Checked 2026-10-06 · 14 references not checked yet
Overview
AI snapshot
Written from the paper’s full text.
TL;DR
The paper proposes qubit networks that achieve perfect transfer of an arbitrary quantum state in a fixed time without switching qubit couplings. It shows perfect transfer in hypercubes and, with engineered fixed couplings, over arbitrarily long linear chains.
Key findings
- Perfect state transfer is possible between antipodes of one-link and two-link hypercubes, with constant transfer times \(t=\pi/2\) and \(t=\pi/\sqrt{2}\), respectively, independent of dimension.
- For \(N\)-qubit spin networks with identical couplings, the maximal perfect communication distance for hypercube geometries is \(2\log_3 N\); perfect transfer between antipodes of \(N\)-link hypercubes for \(N\ge 3\) is impossible.
- In an XY linear chain, perfect transfer occurs only for \(N=2\) and \(N=3\), with amplitudes \(F(t)=-i\sin(t)\) and \(F(t)=-[\sin(t\sqrt{2})]^2\); no perfect transfer occurs for \(N\ge 4\).
- With fixed but engineered couplings \(J_n=\frac{\lambda}{2}\sqrt{n(N-n)}\), perfect transfer over a chain of any length occurs in constant time \(t=\pi/\lambda\); a Heisenberg model with local magnetic fields can give the same dynamics.
Methods
- Theoretical analysis of continuous-time quantum walks on graphs: the network is a graph \(G\) with adjacency matrix \(A(G)\), and state-transfer dynamics is confined to the \(N\)-dimensional single-excitation subspace \(S_G\), where the Hamiltonian equals \(A(G)\).
- Perfect transfer is assessed via the amplitude \(F(t)=\langle N|e^{-iH_G t}|1\rangle\), with perfect transfer when \(|F(t)|=1\).
- The paper diagonalizes the XY linear chain, uses Cartesian products of two- and three-qubit chains to build hypercubes, and maps an engineered chain to a fictitious spin-\((N-1)/2\) particle governed by \(H=\lambda S_x\). No experimental data are used.
Limitations
- Stated: “we do not consider the effects of any other source of errors in this paper”; the paper also calls it an open problem whether an identical-coupling network can exceed the \(2\log_3 N\) distance.
- Stated: perfect transfer in an unmodulated XY linear chain is limited to \(N=2,3\), and perfect transfer between antipodes of \(N\)-link hypercubes for \(N\ge 3\) is impossible.
- Evident from the text: the scheme assumes idealized time-independent Hamiltonians and no dynamical control, requires pre-engineering couplings for arbitrary-length chains, and provides no experimental implementation or error analysis.
Model-written summary. Check it against the paper before relying on it.
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Claims the paper makes
0 of 4 cited sources checked · 0 supported · 0 flagged
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“When restricted to N -qubit spin networks of identical qubit couplings, we show that 2 log 3 N is the maximal perfect communication distance for hypercube geometries.”
- Also stated in: § Perfect state transfer in quantum spin networks · p. 3 · boosted
“Thus we have shown that for a two-link hypercube of N sites, the maximum distance of perfect quantum communication is 2 log 3 N .”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Also stated in: § Perfect state transfer in quantum spin networks · p. 3 · boosted
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“if one allows fixed but different couplings between the qubits then perfect state transfer can be achieved over arbitrarily long distances in a linear chain.”
- Also stated in: § Perfect state transfer in quantum spin networks · p. 4 · boosted
“In addition, we have shown that a quantum state can be transferred perfectly over a chain of any length as long as one can pre-engineer inter-qubit interactions.”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Also stated in: § Perfect state transfer in quantum spin networks · p. 4 · boosted
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Perfect state transfer from one end of the chain to another is possible only for N = 2 and N = 3, with F ( t ) = -i sin( t ) and F ( t ) = -[ sin ( t √ 2 )] 2 respectively.”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“We propose a class of qubit networks that admit perfect transfer of any quantum state in a fixed period of time.”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“This means that the state | 1 〉 ≡ | 1 A 00 · · · 00 B 〉 must evolve into a superposition of states with exactly one spin 'up' and all other spins 'down'.”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“the same as in the engineered chain.”
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The above matrix, Eq. (13), is identical to the representation of the Hamiltonian H of a fictitious spin S = 1 2 ( N -1) particle: H = λS x , where S x is its angular momentum operator and λ is some constant.”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The coefficient α does not change in time, as | 0 〉 is the zero-energy eigenstate of H G .”
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“with corresponding eigenvalues E k = -2 cos kπ N +1 for all k = 1 , . . . , N .”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The d -fold Cartesian product of a one-link chain (two qubits) and a two-link chain (three qubits) lead to onelink and two-link hypercubes with | F ( t ) | given, respectively, by”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes
- It may state two separate claims as one. 6
- Probably not a substantial claim. 6
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Perfect state transfer from one end of the chain to another is possible only for N = 2 and N = 3, with F ( t ) = -i sin( t ) and F ( t ) = -[ sin ( t √ 2 )] 2 respectively.”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
In the paper
“Any quantum state can be perfectly transferred between the two antipodes of the one-link and two-link hypercubes of any dimensions in constant time t = π/ 2 and t = π/ √ 2 respectively [14].”
What the sources say
- Not checked yetcites [14] Note that continuous time quantum walk on the 1-link hypercube has recently been studied by C. Moore and A. Russell in Randomization and Approximation Techniques: 6th International Workshop, (RANDOM 2002), Lecture Notes in Computer Science , (Springer-Verlag, Heidelberg), vol. 2483, p. 164. source
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The Hilbert space H G associated with a network of N qubits is of dimension 2 N .”
Strength:plain· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✗ Based: failsProbably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“commutes with H G , which leads to the conservation of the total z -component of spin.”
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“These tasks can be also accomplished with the Heisenberg, or exchange, interaction by a suitable modulation of the network, e.g., by placing it in a static but, in general, non-uniform external magnetic field.”
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✗ Based: failsProbably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“For fixed N it maximizes the distance between A and B .”
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“An improvement of the perfect quantum communication distance to N is, however, possible if one allows for different, but fixed, couplings between qubits on a chain.”
Strength:hedged· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✗ Based: failsProbably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
In the paper
“The classical mean hitting time between the antipodes in a one-link and two-link d -dimensional hypercube is given, for large d , by 2 d and 3 d , respectively.”
What the sources say
- Not checked yetcites [12] A. Bovier, Markov processes and meta-stability: Lecture notes for the Technical University of Berlin (2003). source
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“It can also be used to transfer or to distribute quantum entanglement.”
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
In the paper
“Quantum communication over short distances through an unmodulated spin chain has been studied in detail, and an expression for the fidelity of quantum state has been obtained [9].”
What the sources say
- Not checked yetcites [9] S. Bose, Phys. Rev. Lett. 91 , 207901 (2003); V. Subrahmanyam, Phys. Rev. A 69 , 034304 (2004). source
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“However, note that we do not consider the effects of any other source of errors in this paper.”
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
The authors state this as an assumption.
Initially all spins point down along a prescribed z-axis, i.e., the network is in the state |0> = |0_A 00...00_B>.
“we shall assume that initially all spins point 'down' along a prescribed z -axis, i.e. the network is in the state | 0 〉 = | 0 A 00 · · · 00 B 〉 .”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
The source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“Inspired by spin chains [100-102] (see figure 12(a)), by tailoring the hopping rates between the waveguides of an array to match the matrix elements of the J x angular momentum operator, such a task becomes possible.”
From Integrated photonic quantum walks (2020) · cites this paper as [102]
Experimental — accuracy not yet measuredIn the citing paper
“From Eq. (5), the evolution time is limited by the minimum energy interval ∆ min ≡ min { ∆ k } , τ ≥ π/ ∆ min , while ˜ τ = π/ ˜ ∆ min .”
From Quantum speed limit for perfect state transfer in one dimension (2006) · cites this paper as [11]
In the citing paper
“This work also implies that quantum algorithms, when implemented in solid state devices, can be optimized, if we employ the concept of spin chain engineering [11].”
From Quantum speed limit for perfect state transfer in one dimension (2006) · cites this paper as [11]
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Claimed chain communication distance counts vertices instead of edges
MinorThe proposed chain has N qubits with its endpoints at opposite ends, so their shortest path has N−1 edges. Under the paper's definition of distance, its perfect communication distance is N−1, not N.
“An improvement of the perfect quantum communication distance to N is, however, possible if one allows for different, but fixed, couplings between qubits on a chain.”
“We define the distance between A and B to be the number of edges constituting the shortest path between them.”
Citations
Cites
Teleporting an unknown quantum state via dual classical and Einstein-Podolsky-Rosen channels
Bennett, C. H., Brassard, G., Crépeau, C., Jozsa, R., Peres, A., & Wootters, W. K. (1993) · Physical Review Letters · doi:10.1103/physrevlett.70.1895 · Cited by 13,703
Quantum computation with quantum dots
Loss, D., & DiVincenzo, D. P. (1998) · Physical Review A · doi:10.1103/physreva.57.120 · Cited by 6,840
Communication via one- and two-particle operators on Einstein-Podolsky-Rosen states
Bennett, C. H., & Wiesner, S. J. (1992) · Physical Review Letters · doi:10.1103/physrevlett.69.2881 · Cited by 5,470
A silicon-based nuclear spin quantum computer
Kane, B. E. (1998) · Nature · doi:10.1038/30156 · Cited by 3,779
Quantum Communication through an Unmodulated Spin Chain
Bose, S. (2003) · Physical Review Letters · doi:10.1103/physrevlett.91.207901 · Cited by 1,407
Experimental demonstration of a robust, high-fidelity geometric two ion-qubit phase gate
Leibfried, D., DeMarco, B., Meyer, V., Lucas, D., Barrett, M., Britton, J., Itano, W. M., Jelenković, B., Langer, C., Rosenband, T., et al. (2003) · Nature · doi:10.1038/nature01492 · Cited by 1,083
Universal quantum computation with the exchange interaction
DiVincenzo, D. P., Bacon, D., Kempe, J., Burkard, G., & Whaley, K. B. (2000) · Nature · doi:10.1038/35042541 · Cited by 924
Realization of the Cirac–Zoller controlled-NOT quantum gate
Schmidt-Kaler, F., Häffner, H., Riebe, M., Gulde, S., Lancaster, G. P. T., Deuschle, T., Becher, C., Roos, C. F., Eschner, J., & Blatt, R. (2003) · Nature · doi:10.1038/nature01494 · Cited by 875
Controlled collisions for multi-particle entanglement of optically trapped atoms
Mandel, O., Greiner, M., Widera, A., Rom, T., Hänsch, T. W., & Bloch, I. (2003) · Nature · doi:10.1038/nature02008 · Cited by 789
A Potentially Realizable Quantum Computer
Lloyd, S. (1993) · Science · doi:10.1126/science.261.5128.1569 · Cited by 649
Flagged first, then by citations
Research works printed but not linked: 3
- 1978, Selected Topics in Graph Theory
- C. Moore, 2002, Randomization and Approximation Techniques: 6th International Workshop
- A. M. Childs, 2003, Proceedings of the 35th ACM Symposium on Theory of Computing (STOC 2003)
Cited by
Sorted by citations
Items 1,001–1,001 of 1,001
Quantum state transfer in a ring geometry of optical waveguides having nonuniform couplings
Beder, I., & Brandão, P. A. (2024) · Physics Letters A · doi:10.1016/j.physleta.2024.129926 · Cited by 1
Metadata
- Authors
- Christandl, M., Datta, N., Ekert, A., & Landahl, A. J.
- Affiliations
- University of Cambridge (GB)
- National University of Singapore (SG)
- Hewlett-Packard (United States) (US)
- Venue
- Physical Review Letters
- Publisher
- American Physical Society (APS)
- Published
- 2004-05-04
- Volume
- 92
- Issue
- 18
- Pages
- 187902-187902
- ISSN
- 0031-9007 (ISSN-L)
- 1079-7114
- OpenAlex
- W2028212109
- Semantic Scholar
- eb739158478cb8205c1ed010d906ee69335abf55
- Cited by
- 1,179
- References
- 22
- Citations by year
- 2026: 48 · 2025: 67 · 2024: 45 · 2023: 57 · 2022: 60 · 2021: 54 · 2020: 57 · 2019: 62 · 2018: 48 · 2017: 47 · 2016: 56 · 2015: 50 · 2014: 54 · 2013: 53 · 2012: 54
- FWCI
- 50.92
- Type
- journal article
- Language
- en
- Open access
- green
- arxiv.org
- Locations
- Physical Review Letters (publishedVersion)
- PubMed (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- National University of Singapore (submittedVersion)
- CERN Document Server (European Organization for Nuclear Research) (submittedVersion)
- arXiv (Cornell University)
- Topics
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum Information and Cryptography
- Physical Sciences › Computer Science › Artificial Intelligence › Quantum Computing Algorithms and Architecture
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum Mechanics and Applications
- Keywords
- perfect state transfer, quantum spin networks, qubit networks, linear chains, quantum communication, quantum computing, qubit coupling, communication distance
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