Ciro Santilli In Ciro's ASCII art circuit diagram notation, it is a loop with three Josephson junctions:
+----X-----+
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+--X----X--+
Superconducting Qubit by NTT SCL (2015)
. Source. Offers an interesting interpretation of superposition in that type of device (TODO precise name, seems to be a flux qubit): current going clockwise or current going counter clockwise at the same time.
Their circuit is a loop with three Josephson junctions, in Ciro's ASCII art circuit diagram notation:
+----X-----+
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+--X----X--+They name the clockwise and counter clockwise states and (named for Left and Right).
When half the magnetic flux quantum is applied as microwaves, this produces the ground state:
where and cancel each other out. And the first excited state is:
Then he mentions that:
- to go from 0 to 1, they apply the difference in energy
- if the duration is reduced by half, it creates a superposition of .
Used e.g. in the Sycamore processor.
The most basic type of transmon is in Ciro's ASCII art circuit diagram notation, an LC circuit e.g. as mentioned at youtu.be/cb_f9KpYipk?t=180 from Video "The transmon qubit by Leo Di Carlo (2018)":
+----------+
| Island 1 |
+----------+
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X C
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+----------+
| Island 2 |
+----------+youtu.be/eZJjQGu85Ps?t=2443 from Video "Superconducting Qubits I Part 1 by Zlatko Minev (2020)" describes a (possibly simplified) physical model of it, as two superconducting metal islands linked up by a Josephson junction marked as
The circuit is then analogous to a LC circuit, with the islands being the capacitor. The Josephson junction functions as a non-linear inductor.
X in the diagram as per-Ciro's ASCII art circuit diagram notation:
+-------+ +-------+
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| Q_1() |---X---| Q_2() |
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+-------+ +-------+Others define it with a SQUID device instead: youtu.be/cb_f9KpYipk?t=328 from Video "The transmon qubit by Leo Di Carlo (2018)". He mentions that this allows tuning the inductive element without creating a new device.
The superconducting transmon qubit as a microwave resonator by Daniel Sank (2021)
. Source. But seriously, this is a valuable little list.
The course is basically exclusively about transmons.
The transmon qubit by Leo Di Carlo (2018)
. Source. Via QuTech Academy.Circuit QED by Leo Di Carlo (2018)
. Source. Via QuTech Academy.Measurements on transmon qubits by Niels Bultink (2018)
. Source. Via QuTech Academy. I wish someone would show some actual equipment running! But this is of interest.Single-qubit gate by Brian Taraskinki (2018)
. Source. Good video! Basically you make a phase rotation by controlling the envelope of a pulse.Two qubit gates by Adriaan Rol (2018)
. Source. Assembling a Quantum Processor by Leo Di Carlo (2018)
. Source. Via QuTech Academy.