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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