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

Acta Physica Polonica A

Entanglement Detection with Non-Ideal Ferromagnetic Detectors

Piotr Rożek, Piotr Busz, Waldemar Kłobus, Damian Tomaszewski, Andrzej Grudka, Andreas Baumgartner, Christian Schönenberger, J. Martinek

Published Feb 1, 2015• 7 citations
Publisher

Abstract

Entangled states are essential in basics quantum communication protocols and quantum cryptography.Ferromagnetic contacts can work as a spin detector, giving possibility of converting information about electron spin to the electric charge, and therefore, detection of entangled states with the electric current measurements is possible.Method of conrming entanglement with non-ideal detectors is presented, the impact of decoherence and noise on states and quality of entanglement is discussed.Entanglement witness (EW) operator method is compared with the CHSH inequalities approach.Required spin polarization for the EW is lower than for the CHSH inequalities.System with asymmetric spin polarizations of detectors was analyzed, including the CHSH inequalities and the EW method.

DOI
10.12693/aphyspola.127.493

Related papers

Entanglement witnessing and quantum cryptography with nonideal ferromagnetic detectors

Waldemar Kłobus, Andrzej Grudka, Andreas Baumgartner +3 more

We investigate theoretically the use of nonideal ferromagnetic contacts as a means to detect quantum entanglement of electron spins in transport experiments. We use a designated entanglement witness and find a minimal spin polarization of $\ensuremath{\eta}>1/\sqrt{3}\ensuremath{\approx}58%$ required to demonstrate spin entanglement. This is significantly less stringent than the ubiquitous tests of Bell's inequality with $\ensuremath{\eta}>1/\sqrt[4]{2}\ensuremath{\approx}84%$. In addition, we discuss the impact of decoherence and noise on entanglement detection and apply the presented framework to a simple quantum cryptography protocol. Our results are directly applicable to a large variety of experiments.

arXiv:1310.5640•Physical Review B•Mar 5, 2014•47 citations

Entanglement Detection by Current Measurements in Double Quantum Dot System

Piotr Busz, Piotr Rożek, Damian Tomaszewski +1 more

The development of quantum computing in quantum dots systems requires highly ecient and continuous solidstate source of spatially separated spin-entangled electrons.One of the approaches is a use of double quantum dot system connected to superconducting lead, where Cooper pairs provide a source of naturally entangled electrons.Apart from the source, an useful tool for detection of quantum entanglement is needed.We present entanglement detection by the ferromagnetic electrodes using entanglement witness operator method and direct measurement of spin polarized current in the system.We investigate requirements that have to be fullled by ferromagnetic detectors.

Acta Physica Polonica A•Feb 1, 2015•8 citations

Full counting statistics of generic spin entangler with quantum dot-ferromagnet detectors

O. Malkoc, C. Bergenfeldt, Peter Samuelsson

Entanglement between spatially separated electrons in nanoscale transport is a fundamental property, yet to be demonstrated experimentally. Here we propose and analyse theoretically the transport statistics of a generic spin entangler coupled to a hybrid quantum dot-ferromagnet detector system. We show that the full distribution of charges arriving at the ferromagnetic terminals provides complete information on the spin state of the particles emitted by the entangler. This provides means for spin entanglement detection via electrical current correlations, with optimal measurement strategies depending on the a priori knowledge of ferromagnet polarization and spin-flip rates in the detector dots. The scheme is exemplified by applying it to Andreev and triple dot entanglers.

arXiv:1312.3982•Europhysics Letters (EPL)•Feb 1, 2014•8 citations

Entanglement detection in Cooper pair splitters from dc current measurements without the efficiency limit of magnetic detectors

Piotr Busz, Damian Tomaszewski, J. Martinek

We present theoretical studies on models for experimental determination of spin correlations and detection of quantum entanglement of spatially separated electrons of Cooper pairs. These models are based on both electric current cross-correlations and simpler dc current measurements. By proper optimization of the entanglement witness method, we demonstrate that entanglement detection is possible with any magnetic detectors regardless of their efficiency. This allows us to break the relatively high previously established limit of detector efficiency (spin polarization), $p>1/\sqrt{3}\ensuremath{\approx}58%$.

Physical review. B./Physical review. B•May 23, 2025•0 citations

Entanglement detection for electrons via witness operators

Lara Faoro, Fabio Taddei

We discuss an implementation of the entanglement witness, a method to detect entanglement with few local measurements, in systems where entangled electrons are generated both in the spin and orbital degrees of freedom. We address the efficiency of this method in various setups, including two different particle-hole entanglement structures, and we demonstrate that it can also be used to infer information on the possible dephasing afflicting the devices.

arXiv:cond-mat/0607645•Physical Review B•Apr 30, 2007•14 citations

Spin entanglement generation and detection in semiconductor nanostructures

Wolfgang Belzig, Adam Bednorz

Entanglement, viz. the non‐separability of quantum states, is a fundamental prediction of quantum mechanics, which is at odds with the classical perception of reality. Furthermore, it constitutes a resource for quantum computation and quantum communication. Electronic degrees of freedom in nanostructures –in particular the spin –constitute promising candidates to implement quantum information architectures in scalable solid state circuits. In this topical review, we will summarize some efforts to create and detect entanglement in such structures. We concentrate first on entanglement in double quantum dots, since they promise to be viable candidates to produce entanglement by confining electrons to a small interaction region. The quantitative detection of the entanglement through transport measurements can be done via current and noise. Secondly, we concentrate on the creation of spin entanglement at quantum point contacts, which has the advantage that the two electrons are automatically spatially separated. We discuss the possibility of performing a Bell test of non‐local correlations. However, as we will point out, a reliable entanglement detection can be performed by current‐correlation measurements, although they require some trust in the experimental setup. Finally, we present a hierarchy of mesoscopic Bell tests, which could be useful to evaluate theoretical proposals and experimental setups.

physica status solidi (b)•Feb 16, 2014•8 citations
Entangled states are essential in basics quantum communication protocols and quantum cryptography.Ferromagnetic contacts can work as a spin detector, giving possibility of converting information about electron spin to the electric charge, and therefore, detection of entangled states with the electric current measurements is possible.Method of conrming entanglement with non-ideal detectors is presented, the impact of decoherence and noise on states and quality of entanglement is discussed.Entanglement witness (EW) operator method is compared with the CHSH inequalities approach.Required spin polarization for the EW is lower than for the CHSH inequalities.System with asymmetric spin polarizations of detectors was analyzed, including the CHSH inequalities and the EW method.
We investigate theoretically the use of nonideal ferromagnetic contacts as a means to detect quantum entanglement of electron spins in transport experiments. We use a designated entanglement witness and find a minimal spin polarization of $\ensuremath{\eta}>1/\sqrt{3}\ensuremath{\approx}58%$ required to demonstrate spin entanglement. This is significantly less stringent than the ubiquitous tests of Bell's inequality with $\ensuremath{\eta}>1/\sqrt[4]{2}\ensuremath{\approx}84%$. In addition, we discuss the impact of decoherence and noise on entanglement detection and apply the presented framework to a simple quantum cryptography protocol. Our results are directly applicable to a large variety of experiments.
The development of quantum computing in quantum dots systems requires highly ecient and continuous solidstate source of spatially separated spin-entangled electrons.One of the approaches is a use of double quantum dot system connected to superconducting lead, where Cooper pairs provide a source of naturally entangled electrons.Apart from the source, an useful tool for detection of quantum entanglement is needed.We present entanglement detection by the ferromagnetic electrodes using entanglement witness operator method and direct measurement of spin polarized current in the system.We investigate requirements that have to be fullled by ferromagnetic detectors.
Entanglement between spatially separated electrons in nanoscale transport is a fundamental property, yet to be demonstrated experimentally. Here we propose and analyse theoretically the transport statistics of a generic spin entangler coupled to a hybrid quantum dot-ferromagnet detector system. We show that the full distribution of charges arriving at the ferromagnetic terminals provides complete information on the spin state of the particles emitted by the entangler. This provides means for spin entanglement detection via electrical current correlations, with optimal measurement strategies depending on the a priori knowledge of ferromagnet polarization and spin-flip rates in the detector dots. The scheme is exemplified by applying it to Andreev and triple dot entanglers.
We present theoretical studies on models for experimental determination of spin correlations and detection of quantum entanglement of spatially separated electrons of Cooper pairs. These models are based on both electric current cross-correlations and simpler dc current measurements. By proper optimization of the entanglement witness method, we demonstrate that entanglement detection is possible with any magnetic detectors regardless of their efficiency. This allows us to break the relatively high previously established limit of detector efficiency (spin polarization), $p>1/\sqrt{3}\ensuremath{\approx}58%$.
Entanglement, viz. the non‐separability of quantum states, is a fundamental prediction of quantum mechanics, which is at odds with the classical perception of reality. Furthermore, it constitutes a resource for quantum computation and quantum communication. Electronic degrees of freedom in nanostructures –in particular the spin –constitute promising candidates to implement quantum information architectures in scalable solid state circuits. In this topical review, we will summarize some efforts to create and detect entanglement in such structures. We concentrate first on entanglement in double quantum dots, since they promise to be viable candidates to produce entanglement by confining electrons to a small interaction region. The quantitative detection of the entanglement through transport measurements can be done via current and noise. Secondly, we concentrate on the creation of spin entanglement at quantum point contacts, which has the advantage that the two electrons are automatically spatially separated. We discuss the possibility of performing a Bell test of non‐local correlations. However, as we will point out, a reliable entanglement detection can be performed by current‐correlation measurements, although they require some trust in the experimental setup. Finally, we present a hierarchy of mesoscopic Bell tests, which could be useful to evaluate theoretical proposals and experimental setups.