Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review Letters

Pseudoentanglement of Spin States in the Multilevel N15@C60 System

M. Mehring, W. Scherer, A. Weidinger

Published Nov 11, 2004• 83 citations
Publisher

Abstract

We have prepared combined electron and nuclear spin pseudoentangled states ${\ensuremath{\Psi}}_{27}^{\ifmmode\pm\else\textpm\fi{}}$ and ${\ensuremath{\Phi}}_{18}^{\ifmmode\pm\else\textpm\fi{}}$ out of the total number of eight quantum states in the multilevel quantum system of a nitrogen atom with electron spin $3/2$ and nuclear spin $1/2$ encaged in the endohedral fullerene $^{15}\mathrm{N}@{\mathrm{C}}_{60}$. Density matrix tomography was applied to verify the degree of entanglement.

DOI
10.1103/physrevlett.93.206603

Related papers

Entangled electron and nuclear spin states in N15@C60: Density matrix tomography

W. Scherer, Michael Mehring

Procedures of the preparation and detection of entangled electron-nuclear spin states in (15)N@C(60) by combining electron spin resonance and electron nuclear double resonance pulse techniques are presented. A quantitative evaluation of the complete density matrix is obtained by a special density matrix tomography. All four Bell states of a two qubit subsystem were analyzed and experimental decoherence times are presented. In addition, we estimate a quantum critical temperature of T(q)=7.76 K for this system at an electron spin resonance frequency of 95 GHz.

The Journal of Chemical Physics•Jan 24, 2008•32 citations

Entanglement of Spin States in 15N@C60

W. Scherer

The endohedral fullerene 15N@C60 comprises an electron spin S = 3/2 coupled to a nuclear spin I = 1/2 and is therefore ideally suited for experimental testing of basic properties of quantum mechanics. We will show that the 15N@C60 molecule represents a multi qubit system where different kinds of entangled states can be generated.

AIP conference proceedings•Jan 1, 2004•0 citations

Density Matrix Tomography of Entangled Electron and Nuclear Spin States in 15N:C60

W. Scherer, Mehring, Michael

We discuss details of the preparation and detection of entangled electron-nuclear spin states in 15N:C60 together with a quantitative evaluation of the complete density matrix. All four Bell states of a two qubit subsystem were analyzed. In addition we find a quantum critical temperature of Tq = 7.73 K for this system at an electron spin resonance frequency of 95 GHz.

arXiv:quant-ph/0602201•Feb 24, 2006•0 citations

Entanglement in P@C60 encapsulated in a solid state matrix

Boris Naydenov, Jens Mende, Wolfgang Harneit +1 more

Abstract This contribution concerns quantum information aspects in fullerenes. In particular we present here the preparation of pseudo‐pure states and pseudo‐entanglement in the coupled electron‐nucleus system P@C60 (S = 3/2 and I = 1/2) encapsulated in a solid state matrix. In this system the degeneracy of the high electron spin is lifted, allowing transition selective excitation. Density matrix tomography and phase rotations are applied for detecting pure states and entanglement The fidelity of the entangled state was determined to F = 0.93. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

physica status solidi (b)•Aug 28, 2008•8 citations

Two-qubit gates between noninteracting qubits in endohedral-fullerene-based quantum computation

Chenyong Ju, Dieter Suter, Jiangfeng Du

We propose a scheme to implement the two-qubit gates between the nuclear spins of the encapsulated atoms in endohedral fullerenes $^{15}\mathrm{N}@{\mathrm{C}}_{60}$ or $^{31}\mathrm{P}@{\mathrm{C}}_{60}$, within today's magnetic resonance techniques. Since there is no interaction between the nuclear spins, this scheme employs the electronic spins as medium and two swap operations are proposed to transfer the information between the nuclear spin $\frac{1}{2}$ and the electronic spin $\frac{3}{2}$, and between two electronic spins $\frac{3}{2}$. These two-qubit gates, along with the single-qubit rotation gates, compose a universal set of quantum gates in fullerene-based quantum computation.

Physical Review A•Jan 17, 2007•55 citations

Entangling nuclear spins using photoexcited triplet states

Vasileia Filidou

Entanglement is one of the most technologically important quantum phenomena and its con-trolled creation brings us a step closer to the realisation of a quantum computer. Hybrid electron and nuclear spin systems which combine long nuclear decoherence times with the high polarisation and rapid processing times of electron spins are considered reliable candidates for the representation of the fundamental building block of a quantum computer, the qubit. In the literature electron spins quite often play the role of a mediator which can access, manipulate and couple states with long coherence times, beneficial for storing quantum information. Despite the fact that an electron spin can be a useful resource for nuclear spin systems, its permanent presence can be a source of decoherence. The use of transient photoexcited electron spins provide an additional advantage and once the operations which involve the electron spin are completed, the electron spin can decay and not interfere further with the evolution of the system. In this thesis we report magnetic resonance experiments and density functional theory calculations for the demonstration of nuclear - nuclear entanglement using photoexcited triplet states. We study homonuclear and heteronuclear fullerene derivatives and we identify in each case the relevant parameters that can lead to high fidelity entangling operations. The hyperfine interaction in a homonuclear system is the key parameter which determines the degree of entanglement between the nucelar spins according to a recent theoretical proposal. We measure and calculate the hyperfine interaction in homonuclear systems with 13C nuclear spins in order to prove the feasibility of this scheme. Further experiments on a fullerene system with two nuclear spins a 31P and a 1H show that entangling operations of high fidelity which involve the demonstration of CNOT gates, are possible within the lifetime of the triplet state.

•Jan 1, 2012•0 citations
We have prepared combined electron and nuclear spin pseudoentangled states \ensuremathΨ27\ifmmode±\else\textpm\fi{\ensuremath{\Psi}}_{27}^{\ifmmode\pm\else\textpm\fi{}}\ensuremathΨ27\ifmmode±\else\textpm\fi​ and \ensuremathΦ18\ifmmode±\else\textpm\fi{\ensuremath{\Phi}}_{18}^{\ifmmode\pm\else\textpm\fi{}}\ensuremathΦ18\ifmmode±\else\textpm\fi​ out of the total number of eight quantum states in the multilevel quantum system of a nitrogen atom with electron spin 3/23/23/2 and nuclear spin 1/21/21/2 encaged in the endohedral fullerene 15N@C60^{15}\mathrm{N}@{\mathrm{C}}_{60}15N@C60​. Density matrix tomography was applied to verify the degree of entanglement.
Procedures of the preparation and detection of entangled electron-nuclear spin states in (15)N@C(60) by combining electron spin resonance and electron nuclear double resonance pulse techniques are presented. A quantitative evaluation of the complete density matrix is obtained by a special density matrix tomography. All four Bell states of a two qubit subsystem were analyzed and experimental decoherence times are presented. In addition, we estimate a quantum critical temperature of T(q)=7.76 K for this system at an electron spin resonance frequency of 95 GHz.
Abstract This contribution concerns quantum information aspects in fullerenes. In particular we present here the preparation of pseudo‐pure states and pseudo‐entanglement in the coupled electron‐nucleus system P@C60 (S = 3/2 and I = 1/2) encapsulated in a solid state matrix. In this system the degeneracy of the high electron spin is lifted, allowing transition selective excitation. Density matrix tomography and phase rotations are applied for detecting pure states and entanglement The fidelity of the entangled state was determined to F = 0.93. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
We propose a scheme to implement the two-qubit gates between the nuclear spins of the encapsulated atoms in endohedral fullerenes 15N@C60^{15}\mathrm{N}@{\mathrm{C}}_{60}15N@C60​ or 31P@C60^{31}\mathrm{P}@{\mathrm{C}}_{60}31P@C60​, within today's magnetic resonance techniques. Since there is no interaction between the nuclear spins, this scheme employs the electronic spins as medium and two swap operations are proposed to transfer the information between the nuclear spin 12\frac{1}{2}21​ and the electronic spin 32\frac{3}{2}23​, and between two electronic spins 32\frac{3}{2}23​. These two-qubit gates, along with the single-qubit rotation gates, compose a universal set of quantum gates in fullerene-based quantum computation.
Entanglement is one of the most technologically important quantum phenomena and its con-trolled creation brings us a step closer to the realisation of a quantum computer. Hybrid electron and nuclear spin systems which combine long nuclear decoherence times with the high polarisation and rapid processing times of electron spins are considered reliable candidates for the representation of the fundamental building block of a quantum computer, the qubit. In the literature electron spins quite often play the role of a mediator which can access, manipulate and couple states with long coherence times, beneficial for storing quantum information. Despite the fact that an electron spin can be a useful resource for nuclear spin systems, its permanent presence can be a source of decoherence. The use of transient photoexcited electron spins provide an additional advantage and once the operations which involve the electron spin are completed, the electron spin can decay and not interfere further with the evolution of the system. In this thesis we report magnetic resonance experiments and density functional theory calculations for the demonstration of nuclear - nuclear entanglement using photoexcited triplet states. We study homonuclear and heteronuclear fullerene derivatives and we identify in each case the relevant parameters that can lead to high fidelity entangling operations. The hyperfine interaction in a homonuclear system is the key parameter which determines the degree of entanglement between the nucelar spins according to a recent theoretical proposal. We measure and calculate the hyperfine interaction in homonuclear systems with 13C nuclear spins in order to prove the feasibility of this scheme. Further experiments on a fullerene system with two nuclear spins a 31P and a 1H show that entangling operations of high fidelity which involve the demonstration of CNOT gates, are possible within the lifetime of the triplet state.