We discuss possibilities of utilizing superconductors with Cooper condensates in triplet pairing states (where the spin of condensate pairs is S=1) for practical realization of quantum computers. Superconductors with triplet pairing condensates have features that are unique and cannot be found in the usual (singlet pairing, S=0) superconductors. The symmetry of the order parameter in some triplet superconductors (e.g., ruthenates) corresponds to doubly-degenerate chiral states. These states can serve as qubit base states for quantum computing.We discuss possibilities of utilizing superconductors with Cooper condensates in triplet pairing states (where the spin of condensate pairs is S=1) for practical realization of quantum computers. Superconductors with triplet pairing condensates have features that are unique and cannot be found in the usual (singlet pairing, S=0) superconductors. The symmetry of the order parameter in some triplet superconductors (e.g., ruthenates) corresponds to doubly-degenerate chiral states. These states can serve as qubit base states for quantum computing.

arXiv:quant-ph/0207098IEEE Transactions on Applied SuperconductivityJun 1, 20035 citations

Towards a theory of superconductivity based on collective Cooper pairs

Carlos Ramírez García, Chumín Wang

Journal of Physics and Chemistry of SolidsOct 18, 20102 citations

Anisotropic purity of entangled photons from Cooper pairs in heterostructures

Jacob S. Gordon, Hae‐Young Kee

It was theoretically proposed that a forward-biased $p\ensuremath{-}n$ junction with a superconducting layer (P-N-S) would produce pure, polarization-entangled photons due to inherent spin-singlet pairing of electrons. However, any heterostructure interface generically induces Rashba spin-orbit coupling, which in turn generates a mixed singlet-triplet superconducting order parameter. Here we study the effect of triplet pairing on the purity of photons produced through Cooper pair recombination. A unique directional dependence of the state purity is found for a triplet superconductor with fixed $\mathbit{d}$: pure, entangled photons are produced when the photon polarization axis is parallel to $\mathbit{d}$. Induced triplet pairing in a singlet superconductor is shown to degrade the state purity, while induced singlet pairing in a triplet superconductor is shown to enhance the production of entangled pairs. These considerations may aid the design of functional devices to produce entangled photons.It was theoretically proposed that a forward-biased $p\ensuremath{-}n$ junction with a superconducting layer (P-N-S) would produce pure, polarization-entangled photons due to inherent spin-singlet pairing of electrons. However, any heterostructure interface generically induces Rashba spin-orbit coupling, which in turn generates a mixed singlet-triplet superconducting order parameter. Here we study the effect of triplet pairing on the purity of photons produced through Cooper pair recombination. A unique directional dependence of the state purity is found for a triplet superconductor with fixed $\mathbit{d}$: pure, entangled photons are produced when the photon polarization axis is parallel to $\mathbit{d}$. Induced triplet pairing in a singlet superconductor is shown to degrade the state purity, while induced singlet pairing in a triplet superconductor is shown to enhance the production of entangled pairs. These considerations may aid the design of functional devices to produce entangled photons.

arXiv:1807.07980Physical review. B./Physical review. BSep 18, 20181 citation

Chirality and spin transformation of triplet Cooper pairs upon interaction with singlet condensate

Andreas Moor, Anatoly Fjodorovich Volkov, K. B. Efetov

We show that the fully polarized triplet $s$ -wave component is characterized not only by the spin direction, but also by chirality. Interaction of a polarized triplet component and a singlet one results in creation of triplet Cooper pairs with opposite spin direction or of different chiralities. Such spin transformation leads to interesting phenomena in multiterminal magnetic Josephson junctions. We calculate the dc Josephson current ${I}_{\text{J}}$ in a multiterminal Josephson contact of the ${S}_{\text{m}}/n/{S}_{\text{m}}^{\ensuremath{'}}$ type with ``magnetic'' superconductors ${S}_{\text{m}}$ that generate fully polarized triplet components. The superconductors ${S}_{\text{m}}$ are attached to magnetic insulators (filters) which let pass electrons with a fixed spin direction only. The filter axes are assumed to be oriented antiparallel to each other. The Josephson current is zero in two-terminal Josephson junction, i.e., in $S/n/{S}_{\text{m}}$ or in ${S}_{\text{m}}/n/{S}_{\text{m}}^{\ensuremath{'}}$ contact. But in the three-terminal Josephson junction, with another $S$ superconductor attached to the normal wire, the finite current ${I}_{\text{J}}$ appears flowing from the $S$ superconductor to ${S}_{\text{m}}$ superconductors. The currents through the right (left) superconductors ${S}_{\text{m}}$ are opposite in sign, ${I}_{\text{R}}\ensuremath{\equiv}{I}_{\text{J}}={I}_{\text{c}}sin({\ensuremath{\chi}}_{\text{R}}+{\ensuremath{\chi}}_{\text{L}}\ensuremath{-}2\ensuremath{\chi})=\ensuremath{-}{I}_{\text{L}}$, where ${\ensuremath{\chi}}_{\text{L/R}}$ and $\ensuremath{\chi}$ are the phases of superconductors ${S}_{\text{m}},{S}_{\text{m}}^{\ensuremath{'}}$, and $S$ , respectively. We discuss possibilities of experimental observation of the effect.We show that the fully polarized triplet $s$-wave component is characterized not only by the spin direction, but also by chirality. Interaction of a polarized triplet component and a singlet one results in creation of triplet Cooper pairs with opposite spin direction or of different chiralities. Such spin transformation leads to interesting phenomena in multiterminal magnetic Josephson junctions. We calculate the dc Josephson current ${I}_{\text{J}}$ in a multiterminal Josephson contact of the ${S}_{\text{m}}/n/{S}_{\text{m}}^{\ensuremath{'}}$ type with ``magnetic'' superconductors ${S}_{\text{m}}$ that generate fully polarized triplet components. The superconductors ${S}_{\text{m}}$ are attached to magnetic insulators (filters) which let pass electrons with a fixed spin direction only. The filter axes are assumed to be oriented antiparallel to each other. The Josephson current is zero in two-terminal Josephson junction, i.e., in $S/n/{S}_{\text{m}}$ or in ${S}_{\text{m}}/n/{S}_{\text{m}}^{\ensuremath{'}}$ contact. But in the three-terminal Josephson junction, with another $S$ superconductor attached to the normal wire, the finite current ${I}_{\text{J}}$ appears flowing from the $S$ superconductor to ${S}_{\text{m}}$ superconductors. The currents through the right (left) superconductors ${S}_{\text{m}}$ are opposite in sign, ${I}_{\text{R}}\ensuremath{\equiv}{I}_{\text{J}}={I}_{\text{c}}sin({\ensuremath{\chi}}_{\text{R}}+{\ensuremath{\chi}}_{\text{L}}\ensuremath{-}2\ensuremath{\chi})=\ensuremath{-}{I}_{\text{L}}$, where ${\ensuremath{\chi}}_{\text{L/R}}$ and $\ensuremath{\chi}$ are the phases of superconductors ${S}_{\text{m}},{S}_{\text{m}}^{\ensuremath{'}}$, and $S$, respectively. We discuss possibilities of experimental observation of the effect.

Physical Review BDec 15, 201519 citations

A Complete Pairing Mechanism in Superconductivity.

J. D. Fan, Y. M. Malozovsky

APSMar 1, 19960 citations

We show that the fully polarized triplet

s

-wave component is characterized not only by the spin direction, but also by chirality. Interaction of a polarized triplet component and a singlet one results in creation of triplet Cooper pairs with opposite spin direction or of different chiralities. Such spin transformation leads to interesting phenomena in multiterminal magnetic Josephson junctions. We calculate the dc Josephson current

{I}_{\text{J}}

in a multiterminal Josephson contact of the ${S}_{\text{m}}/n/{S}_{\text{m}}^{\ensuremath{'}}$ type with ``magnetic'' superconductors

{S}_{\text{m}}

that generate fully polarized triplet components. The superconductors

{S}_{\text{m}}

are attached to magnetic insulators (filters) which let pass electrons with a fixed spin direction only. The filter axes are assumed to be oriented antiparallel to each other. The Josephson current is zero in two-terminal Josephson junction, i.e., in

S/n/{S}_{\text{m}}

or in ${S}_{\text{m}}/n/{S}_{\text{m}}^{\ensuremath{'}}$ contact. But in the three-terminal Josephson junction, with another

S

superconductor attached to the normal wire, the finite current

{I}_{\text{J}}

appears flowing from the

S

superconductor to

{S}_{\text{m}}

superconductors. The currents through the right (left) superconductors

{S}_{\text{m}}

are opposite in sign, ${I}_{\text{R}}\ensuremath{\equiv}{I}_{\text{J}}={I}_{\text{c}}sin({\ensuremath{\chi}}_{\text{R}}+{\ensuremath{\chi}}_{\text{L}}\ensuremath{-}2\ensuremath{\chi})=\ensuremath{-}{I}_{\text{L}}$, where ${\ensuremath{\chi}}_{\text{L/R}}$ and $\ensuremath{\chi}$ are the phases of superconductors ${S}_{\text{m}},{S}_{\text{m}}^{\ensuremath{'}}$, and

S

, respectively. We discuss possibilities of experimental observation of the effect.