Ciro's ASCII art circuit diagram notation Updated +Created
This notation is designed to be relatively easy to write. This is achieved by not drawing ultra complex ASCII art boxes of every component. It would be slightly more readable if we did that, but prioritizing the writer here.
Two wires are only joined if + is given. E.g. the following two wires are not joined:
  |
--|--
  |
but the following are:
  |
--+--
  |
Simple symmetric components:
  • -, + and |: wire
  • AC: AC source. Parameters:
    • Hz: frequency
    • V: peak voltage
    e.g.:
    AC_1Hz_2V
    If only one side is given, the other is assumed to be at a ground G.
  • C: capacitor
  • G: ground. Often used together with DC, e.g.:
    DC_10---R_10---G
    means applying a voltage of 10 V across a 10 Ohm resistor, which would lead to a current of 1 A
  • L: inductor
  • MICROPHONE. As a multi-letter symmetric component, you can connect the two wires anywhere, e.g.
    ---MICROPHONE---
    or:
    |
    MICROPHONE
        |
  • SPEAKER
  • R: resistor
  • SQUID: SQUID device
  • X: Josephson junction
Asymmetric components have multiple letters indicating different ports. The capital letter indicates the device, and lower case letters the ports. The wires then go into the ports:
  • D: diode
    • a: anode (where electrons can come in from)
    • c: cathode
    Sample usage in a circuit:
    --aDc--
    Can also be used vertically like aany other circuit:
    |
    a
    D
    c
    |
    We can also change the port order, the device is still the same due to capital D:
    --cDa--
    
     |
    Dac--
    
     |
    Dca--
    
       |
    --caD
  • DC DC source. Ports:
    • p: positive
    • n: negative
    E.g. a 10 V source with a 10 Ohm resistor would be:
    +---pDC_10_n---+
    |              |
    +----R_10------+
    If only one side is given, the other is assumed to be at a the ground G. We can also omit p and m in that case and assume that p is the one used, e.g. the above would be equivalent to:
    DC_10---R_10---G
    If the voltage is not given, it is assumed to be a potentiometer.
  • T: transistor. The ports are sgTd:
    • s: source
    • g: gate
    • d: gate
    Sample usage in a circuit:
    ---+
       |
    --sgTd--
    All the following are also equivalent:
       |
       g
    --sTd--
    
        |
    --Tsgd--
       |
  • I: electric current source. Ports:
    • s: electron source
    • d: electron destination
  • V: Voltmeter. Ports:
    • p: positive
    • n: negative
    If we don't need to specify explicit positive and negative sides, we can just use:
    ---V---
    without any ports. This is notably often the case for AC circuits.
    Optionaly, we can also add the sides as in:
Numbers characterizing components are put just next to each component with an underscore. When there is only one parameter, standard units are assumed, e.g.:
+-----+
|     |
C_1p  R_2k
|     |
+-----+
means:
  • a capacitor with 1 pico Faraday
  • a resistor with 2 k Ohms
Micro is denoted as u.
Wires can just freely come in and out of specs of a component, they are then just connected to the component, e.g.:
DC_10---R_10---G
means applying a voltage of 10 V across a 10 Ohm resistor, which would lead to a current of 1 A
If a component has more than two parameters, units are used to distinguish them when possible, e.g.:
AC_1kV_2MHz
means an AC source with:
LC circuit Updated +Created
When Ciro Santilli was studying electronics at the University of São Paulo, the courses, which were heavily inspired from the USA 50's were obsessed by this one! Thinking about it, it is kind of a cool thing though.
Video 1.
Tutorial on LC resonant circuits by w2aew (2012)
Source.
Video 2.
LC circuit dampened oscillations on an oscilloscope by Queuerious Guy (2014)
Source. Finally a video that shows the oscillations without a driving AC source. The dude just move wires around on his breadboard manually, first charging the capacitor and then closing the LC circuit, and is able to see damped oscillations on the oscilloscope.
Video 3.
Introduction to LC Oscillators by USAF (1974)
Source.
Video 4. Source. Exactly what you would expect from an Eugene Khutoryansky video. The key insight is that the inductor resists to changes in current. So when current is zero, it slows down the current. And when current is high, it tries to keep it going, which recharges the other side of the capacitor.
Superconducting quantum computer need non-linear components Updated +Created
Non-linearity is needed otherwise the input energy would just make the state go to higher and higher energy levels, e.g. from 1 to 2. But we only want to use levels 0 and 1.
The way this is modelled in by starting from a pure LC circuit, which is an harmonic oscillator, see also quantum LC circuit, and then replacing the linear inductor with a SQUID device, e.g. mentioned at: youtu.be/eZJjQGu85Ps?t=1655 Video "Superconducting Qubits I Part 1 by Zlatko Minev (2020)".
Transmon Updated +Created
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 |
+----------+
   |   |
   X   C
   |   |
+----------+
| 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 X in the diagram as per-Ciro's ASCII art circuit diagram notation:
+-------+       +-------+
|       |       |       |
| Q_1() |---X---| Q_2() |
|       |       |       |
+-------+       +-------+
The circuit is then analogous to a LC circuit, with the islands being the capacitor. The Josephson junction functions as a non-linear inductor.
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.
Video 1.
The superconducting transmon qubit as a microwave resonator by Daniel Sank (2021)
Source.
Video 2.
Calibration of Transmon Superconducting Qubits by Stefan Titus (2021)
Source. Possibly this Keysight which would make sense.