---
title: "EPIQUANTI : Types de Qubits"
date: 2021-10-26 14:00
categories: [tronc commun S9, EPIQUANTI]
tags: [tronc commun, EPIQUANTI, S9]
math: true
---
Lien de la [note Hackmd](https://hackmd.io/@lemasymasa/SJwq0DBLF)

Lien du [livre du prof](https://www.oezratty.net/wordpress/2021/understanding-quantum-technologies-2021/)

[Slide du cours](https://www.oezratty.net/Files/Work/Olivier%20Ezratty%20Quantique%20EPITA%204%20Oct2021.pdf)


# Quantum anneleaing

$$
\mathcal H_p =
\sum_{i=0}^Nh_i\sigma_i^Z+\sum_{i,j=0}^NJ_{ij}\sigma_i^Z\sigma_j^Z
$$

## Jargon


## D Wave

**Super conducting quantum annealing**

15 ans d'avance sur la creation de ses machines

:::info
- **Spin up** qubit $\vert\uparrow\rangle$
- **Spin up** qubit $\vert\downarrow\rangle$
:::


## Quantum annealing and ising model

$$
\mathcal H_p =\sum_{i=0}^Nh_i\sigma_i^Z+\sum_{i\lt j}^NJ_{ij}\sigma_i^Z\sigma_j^Z
$$

- $\mathcal H_p$: system hamiltonian
- $h_i$: energy difference between 2 states of qubits i
- $v_i$: vertices containing qubit i
- $J_{ij}$: coupling between vertices $v_i$ et $v_j$ with close i and j
- $E$: edge, connecting qubits

### Computing process


Starts with converting the probleme into a Ising model or QUBO (Quadratic Unconstrained Binary Optimization)
1. Initialization of qubits states to $\vert\uparrow\rangle$ or $\vert\downarrow\rangle$
2. Setting qubits bias levels $h_i$
3. Slowly growing $J_{ij}$ coupling
4. System converging to minimal $\mathcal H_p$
5. Readout $\vert\uparrow\rangle$ or $\vert\downarrow\rangle$ states for all qubits, giving the solution to the problem of finding the energy minimum for $H_p$



:::info
Le **chimera** est la facon dont les qubits sont relies entre eux physiquement dans le processeur
:::


## Algorithms


## Pegasus / Advantage 2020 generation

**5436 qubits**

Each qubits is connected to 15 neighbour qubits through 37440 couplers, from 6 per qubit in previous generations.

Qubits are operating at 15,8 mK

:::warning
One order of magnitude improvement in time spent solving problems vs D-Wave 2000Q launched in 2017
:::


*Pourquoi c'est plus dur de rajouter de nouveaux qubits ?*
> C'est plus dur a intriquer


# Superconducting qubits



## Qubits operating temperatures rationale

*Pourquoi est-ce qu'on doit les refroidir ces qubits ?*
> On veut eviter la decoherence des qubits mais pas que
> Les micro-ondes qu'on envoie sur les qubits sont conditionnees par le niveau d'energie
> On refroidit pour que le bruit ambiant soit inferieur a la puissance des micro-ondes


## 5 Superconducting qubits lab configuraiton




## IBM

### Roadmap


## Google



## Google’s 1 million physical qubits plan


> C'est quoi la consommation energetique ? - Theotime

## Alice & Bob

:::info
French startup created by Théau Peronnin and Raphaël
Lescanne, from ENS
:::
> with the help from Benjamin Huard (ENS Lyon), Zaki
Leghtas (ENS Paris), Mazyar Mirrahmi (Inria), Philippe
Campagne-Ibarcq (Inria) and Emmanuel Flurin (CEA)

- use cat-qubits based on two photons coupling in a cavity to increase reliability of superconducting qubits
- qubit information comes from measuring cavity photon number parity without measuring photon number
- expect to build a logical superconducting qubit with only 30 cat-qubits instead of 10 000 classical superconducting qubits
- significantly reduce the burden to create a LSQ FTQC (large scale quantum / fault tolerant quantum computer)
- plan to produce a first processor with logical qubits by 2023


## Amazon

:::info
Amazon announced in december 2020 it will build its own quantum computers using cat-qubits superconducting, in a 118 pages theoretical paper
:::

> it plans to use surface codes QEC

it’s partnering with Caltech (incl John Preskill), Yale (Devoret/Schoelkopf teams)
and other universities


## Summary


# Electron spins qubits

## Different electron spins qubit platforms


## How to detect a single charge?


## How to manipulate a single spin?


## How to realize a two-qubit gate?


## State of the art of two qubit gates



planar systems with a huge number of electrodes to:
- define the reservoirs - source and drain
- control the height of the barrier between quantum dots
- define the depth of the quantum well
- manipulate the qubits
- read out the qubits

## Toward a scalable platform


## C12 Quantum Electronic

:::info
french startup created by Matthieu and Pierre Desjardins with the help from Taki Kontos (LPENS) electron spins qubits trapped in carbon nanotubes 5 qubits demonstrator planned for 2021/2022
:::



## Summary


# NV centers qubits



## NV centers implementation and controls


## Quantum brillance

:::info
Australian startup
- ambiant temperature qubits
- 5 NV centers qubits demonstrated in 2021
- they plan to scale > 50 qubits in 2022
- fits on a desktop computer form factor
:::



## qubits NV centers


# Topologic qubits

## The topological qubit bit

Chez microsoft:



- better stability qubits
- low decoherence noise
- few errors
- long coherence time
- high gate speed

:::danger
- nothing demonstrated so far
- no prototype
- different algorithms
:::


## Majorana fermions summary


# Trapped ions qubits


## IonQ

:::info
La boite la plus calee et ayant recu le plus de fonds: \$$82$M en 2015

Maryland and Duke Universities spin-off launched by Christopher Monroe
:::



| $\color{green}{\text{pros}}$ | $\color{red}{\text{cons}}$
| -------- | -------- |
| laser controlled gates | slow gates |
| $32$ qubits with a large quantum volume of $2^{22}$ reached in 2020|not easy to scale, planning to network several tiny units (above)
|long coherence time and good qubits fidelity||
|excellent qubit connectivity thanks to phonons||
|available on Microsoft and Amazon cloud services||

:::warning
IPO planned in 2021
:::

## Honeywell

:::info
- 2D trapped ions announced in march 2020
- 4 qubits in march 2020
- 6 qubits in june 2020
- 10 qubits in septembre 2020
:::

:::success
Better scalability project
:::



## Trapped ions qubits summary


# Cold atoms qubits

## Cold atoms and Rydberg states


:::info
**Etat de Rydberg**: etat tres energisant
:::


## Cold atoms qubits summary


# Photon qubits

## Photons qubits types and tools

Qubits


Instrumentation




## Quantum dot photon source


## Quantum dot photon source



## DV and CV photon qubits



## Photons qubits summary