Comparison of a direct measure of barrier crossing times with indirect measures such as the Larmor time
Different approaches for considering barrier crossing times are analyzed, with special emphasis on recent experiments which attempt to measure what is commonly referred to as the Larmor tunneling time. We show that that these experiments cannot reveal the Larmor time, due to the finite energy width...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2021-01-01
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| Series: | New Journal of Physics |
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| Online Access: | https://doi.org/10.1088/1367-2630/ac047b |
| _version_ | 1797750080015433728 |
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| author | Tom Rivlin Eli Pollak Randall S Dumont |
| author_facet | Tom Rivlin Eli Pollak Randall S Dumont |
| author_sort | Tom Rivlin |
| collection | DOAJ |
| description | Different approaches for considering barrier crossing times are analyzed, with special emphasis on recent experiments which attempt to measure what is commonly referred to as the Larmor tunneling time. We show that that these experiments cannot reveal the Larmor time, due to the finite energy width of the incident particles. The Larmor time, which measures changes in spin polarization, is classified together with other measurements such as the Buttiker–Landauer oscillating barrier time as indirect measurements of interaction times of scattered particles. In contrast, we present a direct quantum mechanical measure of a barrier crossing time taken to be the difference between the mean flight time for a particle transmitted through a potential barrier incident on a screen and the time it would take to reach the same screen without the barrier. These metrics are asymptotic, in the sense that they infer a time from a measurement after the scattering event is over, whereas other measures like the dwell time are local. Some time measures are well-defined only for incident states which are monochromatic in energy, others are well-defined also for incident wavepackets whose incident energy width is finite. In this paper we compare the different approaches to conclude that only the flight time can be used to answer the provocative (but ultimately ill-posed) question: how much time does it take to tunnel through a barrier? |
| first_indexed | 2024-03-12T16:27:33Z |
| format | Article |
| id | doaj.art-7c56a3c62dbd4ddd946bab5f043c9af1 |
| institution | Directory Open Access Journal |
| issn | 1367-2630 |
| language | English |
| last_indexed | 2024-03-12T16:27:33Z |
| publishDate | 2021-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | New Journal of Physics |
| spelling | doaj.art-7c56a3c62dbd4ddd946bab5f043c9af12023-08-08T15:39:24ZengIOP PublishingNew Journal of Physics1367-26302021-01-0123606304410.1088/1367-2630/ac047bComparison of a direct measure of barrier crossing times with indirect measures such as the Larmor timeTom Rivlin0https://orcid.org/0000-0002-9275-2917Eli Pollak1https://orcid.org/0000-0002-5947-4935Randall S Dumont2https://orcid.org/0000-0003-2209-6122Chemical and Biological Physics Department, Weizmann Institute of Science , 76100 Rehovot, IsraelChemical and Biological Physics Department, Weizmann Institute of Science , 76100 Rehovot, IsraelDepartment of Chemistry and Chemical Biology, McMaster University , Hamilton, Ontario L8S 4M1, CanadaDifferent approaches for considering barrier crossing times are analyzed, with special emphasis on recent experiments which attempt to measure what is commonly referred to as the Larmor tunneling time. We show that that these experiments cannot reveal the Larmor time, due to the finite energy width of the incident particles. The Larmor time, which measures changes in spin polarization, is classified together with other measurements such as the Buttiker–Landauer oscillating barrier time as indirect measurements of interaction times of scattered particles. In contrast, we present a direct quantum mechanical measure of a barrier crossing time taken to be the difference between the mean flight time for a particle transmitted through a potential barrier incident on a screen and the time it would take to reach the same screen without the barrier. These metrics are asymptotic, in the sense that they infer a time from a measurement after the scattering event is over, whereas other measures like the dwell time are local. Some time measures are well-defined only for incident states which are monochromatic in energy, others are well-defined also for incident wavepackets whose incident energy width is finite. In this paper we compare the different approaches to conclude that only the flight time can be used to answer the provocative (but ultimately ill-posed) question: how much time does it take to tunnel through a barrier?https://doi.org/10.1088/1367-2630/ac047btunnelingflight timeLarmor timedwell timetime dependent quantum mechanicsquantum theory and foundations |
| spellingShingle | Tom Rivlin Eli Pollak Randall S Dumont Comparison of a direct measure of barrier crossing times with indirect measures such as the Larmor time New Journal of Physics tunneling flight time Larmor time dwell time time dependent quantum mechanics quantum theory and foundations |
| title | Comparison of a direct measure of barrier crossing times with indirect measures such as the Larmor time |
| title_full | Comparison of a direct measure of barrier crossing times with indirect measures such as the Larmor time |
| title_fullStr | Comparison of a direct measure of barrier crossing times with indirect measures such as the Larmor time |
| title_full_unstemmed | Comparison of a direct measure of barrier crossing times with indirect measures such as the Larmor time |
| title_short | Comparison of a direct measure of barrier crossing times with indirect measures such as the Larmor time |
| title_sort | comparison of a direct measure of barrier crossing times with indirect measures such as the larmor time |
| topic | tunneling flight time Larmor time dwell time time dependent quantum mechanics quantum theory and foundations |
| url | https://doi.org/10.1088/1367-2630/ac047b |
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