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States and businesses: the race for quantum computers

Landry Bretheau
Landry Bretheau
Professor at Ecole Polytechnique, Quantum Physicist and Researcher in the Laboratory of Condensed Matter Physics (PMC*)

Pres­i­dent Macron recent­ly announced the French Nation­al ‘Plan Quan­tique’, promis­ing a sum of €1.8 bil­lion to quan­tum research over the next ten years. As a researcher in the field of quan­tum physics, why is the French gov­ern­ment pay­ing so much atten­tion to the field now, specifically? 

Landry Bretheau. It is hap­pen­ing now because it’s the right time – there are many who say we are enter­ing the sec­ond quan­tum rev­o­lu­tion. Bear­ing in mind that the first quan­tum rev­o­lu­tion hap­pened in the 1920–30s, with the work of now house­hold-named sci­en­tists like Ein­stein or Planck. 

Back then it was first a con­cep­tu­al rev­o­lu­tion when we came to under­stand con­cepts like ‘wave-par­ti­cle dual­i­ty’, ‘black-body radi­a­tion’ and ‘light-mat­ter inter­ac­tion’, which until quan­tum physics arrived sci­en­tists couldn’t explain. Their dis­cov­er­ies gave rise to game-chang­ing tech­nolo­gies that moved engi­neer­ing into the dig­i­tal age, like lasers and tran­sis­tors. The lat­ter allow us to con­trol elec­tron­ic sig­nals, an impor­tant tech­nol­o­gy for com­put­er processors. 

There was, how­ev­er, an aspect that was con­fus­ing to researchers – the con­cept of quan­tum entan­gle­ment. With­out going into too much detail, it was unknown for a long time whether the entan­gle­ment they pre­dict­ed was a nat­ur­al phe­nom­e­non or due to a mis­un­der­stand­ing of quan­tum physics. We now know that it is nat­ur­al, thanks to exper­i­ments that were per­formed on indi­vid­ual quan­tum objects, in par­tic­u­lar in the research of Prof. Alain Aspect, a pio­neer in the field. He has actu­al­ly been very instru­men­tal in pro­mot­ing the sec­ond quan­tum rev­o­lu­tion and con­vinc­ing the gov­ern­ment that fund­ing research is a good investment.

What is the sig­nif­i­cance of such a proposal? 

In short, the ‘Plan Quan­tique’ is on the table because there is a promise of new tech­nolo­gies. Now that the phe­nom­e­non of entan­gle­ment has been well estab­lished, it is pos­si­ble to imag­ine future appli­ca­tions using quan­tum tech­nolo­gies for cal­cu­la­tion, com­mu­ni­ca­tions, sens­ing and sim­u­la­tion with poten­tial spin­offs in ener­gy, health and secu­ri­ty. But the main sell­ing point, so to say, is the quan­tum com­put­er.

Many peo­ple will have heard of quan­tum com­put­ers with­out know­ing what they are, and it must be said that the word ‘com­put­er’ is slight­ly mis­lead­ing. It is unlike­ly that we will see a uni­ver­sal quan­tum com­put­er in the future that will replace the PC or smart­phone, for exam­ple. Rather, quan­tum com­put­ers are actu­al­ly super-cal­cu­la­tors, capa­ble of run­ning spe­cif­ic pow­er­ful quan­tum algo­rithms much faster than an ordi­nary processor.

The idea is to exploit quan­tum phe­nom­e­na such as super­po­si­tion and entan­gle­ment to per­form faster com­pu­ta­tion. A quan­tum com­put­er manip­u­lates infor­ma­tion using a large num­ber of quan­tum bits, that can be pre­pared in mas­sive­ly entan­gled states. This allows one to encode mul­ti­ple com­pu­ta­tion­al results in a sin­gle step, in a phe­nom­e­non known as quan­tum par­al­lelism. This can lead to a quan­tum speed-up for spe­cif­ic algo­rithms, such as “prime fac­tori­sa­tion”, which is the basis for RSA encryp­tion. This encryp­tion method is com­mon­ly used for secure data trans­mis­sion in par­tic­u­lar in bank­ing oper­a­tions. Even though crack­ing RSA secu­ri­ty is extreme­ly dif­fi­cult with a stan­dard com­put­er, a quan­tum com­put­er could do it much faster and thus decode encrypt­ed communications.

That is why there is much inter­est in this tech­nol­o­gy, par­tic­u­lar­ly in terms of mil­i­tary defence. If some states have that capa­bil­i­ty, then it could become a mil­i­tary issue. Hence why the US Depart­ment of Defense is heav­i­ly fund­ing a research pro­gram into quan­tum computing. 

Ordinateur Quantique
From left to right: Jean-Damien Pil­let, Landy Bretheau and Ambroise Peugeot

Big tech com­pa­nies like Google and Face­book are already invest­ing in quan­tum com­put­ers, as are the USA and Chi­na. Is there much hope that France will be able to keep up? 

Since 2018 the USA announced a $2bn invest­ment in research and Chi­na is said to have spent at least $10bn on their Nation­al Lab­o­ra­to­ry for Quan­tum Infor­ma­tion Sci­ences. In Europe, fund­ing has been going on for some time now too. Ger­many start­ed their pro­gram three years ago and the EU has been fund­ing the Quan­tum Flag­ship project since 2018, offer­ing €1bn over the next ten years. So, yes, the ‘Plan Quan­tique’, which is based on the high-lev­el research already present in France, will help us to keep up –we weren’t the first but we are very well positioned.

The French pri­vate sec­tor will also be involved too, though. Nation­al and Euro­pean com­pa­nies like Total and Air­bus have promised to invest. And start-ups are pop­ping up across the coun­try; Quan­dela, Pasqal and Alice & Bob, to name but three, are spin­offs from French research lab­o­ra­to­ries. So far, nobody has a ful­ly func­tion­ing quan­tum com­put­er with any mean­ing­ful pro­cess­ing pow­er. Google is among the fur­thest along, with a proces­sor that is lim­it­ed to 53 quan­tum bits. This is tru­ly an exper­i­men­tal tour de force but it is still too small at the moment for any use­ful application. 

You might say, “oh well let’s just add more qubits to make the proces­sor more pow­er­ful.” But there comes the prob­lem. Quan­tum states are high­ly frag­ile – the more you have, the less sta­ble it becomes. Hence, quan­tum com­put­ers need to be high­ly con­fined, i.e. iso­lat­ed from their envi­ron­ment. This, how­ev­er, in itself cre­ates a para­dox because the more con­fined it is, the hard­er it is for us to actu­al­ly com­mu­ni­cate with the com­put­er to con­trol what it does. 

What will this mean for French research on quan­tum physics? 

It’s not tomor­row that we will have a quan­tum com­put­er. But fund­ing like this is a way of open­ing up our chances and I think it’s a great thing that the mon­ey is being put for­ward. We might not even get a ful­ly oper­at­ing quan­tum com­put­er in ten years, but it is cer­tain that we will dis­cov­er oth­er excit­ing things along the way. And even when we’ll cre­ate one, it is unlike­ly to be an every­day item. Quan­tum com­put­ers will more like­ly be strate­gic tools, enabling spe­cif­ic appli­ca­tions and used for basic research, R&D or gov­ern­ment purposes. 

More­over, inno­va­tions will not only take place on the hard­ware lev­el (i.e. the machines them­selves). There is also a need for new ideas in terms of soft­ware, too. The­o­ret­i­cal research, at the inter­face between physics, com­put­er sci­ence and math­e­mat­ics, must there­fore dis­cov­er new algo­rithms for quan­tum acceleration.

Such fund­ing is very encour­ag­ing for young peo­ple enter­ing the labour mar­ket! It can be help­ful in choos­ing their career and encour­age more to become quan­tum researchers or engi­neers. That being said, it is worth point­ing out that there are already IBM quan­tum com­put­ers acces­si­ble via the cloud. Even if their per­for­mance remains rather lim­it­ed, they allow stu­dents to famil­iarise them­selves with quan­tum com­put­ing, and to car­ry out their first experiences!

Inter­view by James Bowers


Landry Bretheau

Landry Bretheau

Professor at Ecole Polytechnique, Quantum Physicist and Researcher in the Laboratory of Condensed Matter Physics (PMC*)

Landry Bretheau graduated from Ecole polytechnique in 2005 and then completed his Ph.D. at CEA Saclay. Next, he conducted two successive post-docs at ENS (France) and MIT (USA). Since 2017, he has been building-up a new laboratory – QCMX Lab – together with his colleague Jean-Damien Pillet, which explores the physics of Hybrid Quantum Circuits. To develop this new activity, Landry Bretheau was awarded a Young Team Fellowship from l’X, a Young Researcher Grant from the French National Research Agency and an ERC** Starting Grant from the European Research Council. His work has led to major contributions in the fields of Mesoscopic Superconductivity and Quantum Circuits and was awarded the X Thesis Award and the 2020 Nicholas Kurti Science Prize. *PMC: a joint research unit CNRS, École Polytechnique - Institut Polytechnique de Paris. **Under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 947707).

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