A quantum fluctuation description of charge qubits
We consider a specific instance of a superconducting circuit, the so-called charge-qubit, consisting of a capacitor and a Josephson junction that we describe by means of the BCS microscopic model in terms of two tunnelling superconducting systems in the strong-coupling quasi-spin formulation. Then,...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2024-01-01
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| Series: | New Journal of Physics |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1367-2630/ad19ac |
| _version_ | 1797338131083558912 |
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| author | F Benatti F Carollo R Floreanini H Narnhofer F Valiera |
| author_facet | F Benatti F Carollo R Floreanini H Narnhofer F Valiera |
| author_sort | F Benatti |
| collection | DOAJ |
| description | We consider a specific instance of a superconducting circuit, the so-called charge-qubit, consisting of a capacitor and a Josephson junction that we describe by means of the BCS microscopic model in terms of two tunnelling superconducting systems in the strong-coupling quasi-spin formulation. Then, by means of collective observables we derive the Hamiltonian governing the quantum behaviour of the circuit in the limit of a large number N of quasi-spins. Our approach relies on suitable quantum fluctuations , i.e. on collective quasi-spin operators, different from mean-field observables, that retain a quantum character in the large- N limit. These collective operators generate the Heisenberg algebra on the circle and we show that their dynamics reproduces the phenomenological one generated by the charge qubit Hamiltonian obtained by quantizing the macroscopic classical Hamiltonian of the circuit. The microscopic derivation of the emergent, large- N behaviour provides a rigorous setting to investigate more in detail both general quantum circuits and quantum macroscopic scenarios; in particular, in the specific case of charge-qubits, it allows to explicitly obtain the temperature dependence of the critical Josephson current in the strong coupling regime, a result not accessible using standard approximation techniques. |
| first_indexed | 2024-03-08T09:26:35Z |
| format | Article |
| id | doaj.art-0eda36b0e964423db4ee5922b666f027 |
| institution | Directory Open Access Journal |
| issn | 1367-2630 |
| language | English |
| last_indexed | 2024-03-08T09:26:35Z |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | New Journal of Physics |
| spelling | doaj.art-0eda36b0e964423db4ee5922b666f0272024-01-31T08:00:09ZengIOP PublishingNew Journal of Physics1367-26302024-01-0126101305710.1088/1367-2630/ad19acA quantum fluctuation description of charge qubitsF Benatti0https://orcid.org/0000-0002-0712-2057F Carollo1R Floreanini2H Narnhofer3https://orcid.org/0000-0002-6929-4831F Valiera4Dipartimento di Fisica, Università di Trieste , Trieste 34151, Italy; Istituto Nazionale di Fisica Nucleare, Sezione di Trieste , 34151 Trieste, ItalyInstitut für Theoretische Physik, Universität Tübingen , Auf der Morgenstelle 14, 72076 Tübingen, GermanyIstituto Nazionale di Fisica Nucleare, Sezione di Trieste , 34151 Trieste, ItalyFaculty of Physics, University of Wien , A-1091 Vienna, AustriaI. Institut für Theoretische Physik, Universität Hamburg , Notkestraße 9-11, Hamburg 22607, GermanyWe consider a specific instance of a superconducting circuit, the so-called charge-qubit, consisting of a capacitor and a Josephson junction that we describe by means of the BCS microscopic model in terms of two tunnelling superconducting systems in the strong-coupling quasi-spin formulation. Then, by means of collective observables we derive the Hamiltonian governing the quantum behaviour of the circuit in the limit of a large number N of quasi-spins. Our approach relies on suitable quantum fluctuations , i.e. on collective quasi-spin operators, different from mean-field observables, that retain a quantum character in the large- N limit. These collective operators generate the Heisenberg algebra on the circle and we show that their dynamics reproduces the phenomenological one generated by the charge qubit Hamiltonian obtained by quantizing the macroscopic classical Hamiltonian of the circuit. The microscopic derivation of the emergent, large- N behaviour provides a rigorous setting to investigate more in detail both general quantum circuits and quantum macroscopic scenarios; in particular, in the specific case of charge-qubits, it allows to explicitly obtain the temperature dependence of the critical Josephson current in the strong coupling regime, a result not accessible using standard approximation techniques.https://doi.org/10.1088/1367-2630/ad19acJosephson effectcharge qubitsquantum fluctuationsmesoscopic dynamics |
| spellingShingle | F Benatti F Carollo R Floreanini H Narnhofer F Valiera A quantum fluctuation description of charge qubits New Journal of Physics Josephson effect charge qubits quantum fluctuations mesoscopic dynamics |
| title | A quantum fluctuation description of charge qubits |
| title_full | A quantum fluctuation description of charge qubits |
| title_fullStr | A quantum fluctuation description of charge qubits |
| title_full_unstemmed | A quantum fluctuation description of charge qubits |
| title_short | A quantum fluctuation description of charge qubits |
| title_sort | quantum fluctuation description of charge qubits |
| topic | Josephson effect charge qubits quantum fluctuations mesoscopic dynamics |
| url | https://doi.org/10.1088/1367-2630/ad19ac |
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