Health, tech, space: quantum technology is already benefiting many sectors

This art­icle is part of our spe­cial issue « Quantum: the second revolu­tion unfolds ». Read it here

Quantum phys­ics has now largely become part of our every­day lives. The “first quantum revolu­tion” led to a host of devices and tech­niques that we use almost every day. Lasers, elec­tron­ics, LED light­ing, photo­vol­ta­ic pan­els, nuc­le­ar medi­cine – none of these every­day tech­no­lo­gies could be used without a detailed know­ledge of the pro­cesses that take place on an atom­ic level, thanks to an under­stand­ing of the beha­viour of ele­ment­ary particles and the inter­ac­tions between mat­ter and light.

But quantum mech­an­ics has not fin­ished chan­ging our world. The very latest dis­cov­er­ies from research labor­at­or­ies fore­shad­ow a second quantum revolu­tion, in which mas­tery of the pro­cesses at work in the infin­ites­im­al may once again pro­foundly change the way we live, com­mu­nic­ate, and under­stand the world. Let’s take a look at the next applic­a­tions of quantum phys­ics in the indus­tri­al world.

The ever-finer con­trol of elec­tron flows in ever-smal­ler devices has enabled elec­tron­ics to reach unpre­ced­en­ted levels of mini­atur­isa­tion. In 2021, IBM announced the devel­op­ment of a chip made of 2 nano­metre tran­sist­ors, with a dens­ity of 333 mil­lion tran­sist­ors per mm².

But in addi­tion to its elec­tric­al charge, the elec­tron has anoth­er prop­erty called “spin”. This quantum quant­ity has no clas­sic­al equi­val­ent but can be com­pared to a “mag­net­ic moment”, as if the elec­tron were a tiny mag­net rotat­ing on itself. The prin­ciple of spin­tron­ics is there­fore to manip­u­late the spin of elec­trons rather than their elec­tric­al charge in order to cre­ate new applic­a­tions, but also to dra­mat­ic­ally reduce the power con­sump­tion of components.

Spin­tron­ics is already being used in a num­ber of elec­tron­ic com­pon­ents, includ­ing com­puter memory (for which its dis­cover­ers won the Nobel Prize in Phys­ics in 2007) and cer­tain mag­net­ic sensors for cars and robotics.

Spin­tron­ics is already used in a num­ber of elec­tron­ic com­pon­ents, such as com­puter memories.

But, as men­tioned above, the mini­atur­isa­tion of elec­tron­ic devices is so advanced that their basic ele­ments will soon be the size of just a few atoms. A size that will make their beha­viour almost exclus­ively quantum. To read and write on such small memor­ies, a team from the Insti­tut Ray­on­nement-Matière de Saclay (IRa­MiS) has stud­ied the beha­viour of a molecule (called FeTTP) that nor­mally plays a role in the trans­port of oxy­gen by haemo­globin¹.

This molecule depos­ited on graphene (a lay­er of car­bon atoms one atom thick) can change spin eas­ily and at will. This con­sti­tutes a new read/write mech­an­ism for a single molecu­lar spin, which is even smal­ler and more energy-effi­cient than exist­ing devices.

Mean­while, the Nanos­ciences and Nan­o­tech­no­lo­gies Centre at the Uni­ver­sity of Par­is-Saclay is try­ing to make arti­fi­cial intel­li­gence sys­tems more flex­ible². In con­ven­tion­al com­puter sys­tems, the basic inform­a­tion is coded in the form of 0 or 1. New spin­tron­ic sys­tems make it pos­sible to intro­duce nuances into the bin­ary code, such as 0+ or 1- states, and to integ­rate this ‘fuzzy’ logic into arti­fi­cial neur­al net­works, which would oper­ate more like the organ­ic bio­lo­gic­al neur­ons in our brains.

A large num­ber of sensors are built around dif­fer­ent quantum phe­nom­ena that give them the abil­ity to meas­ure minute sig­nals with excel­lent res­ol­u­tion, open­ing up new fields of application.

In a micro­scope, the res­ol­u­tion lim­it is determ­ined by the prop­er­ties of the light used. Gen­er­ally speak­ing, it is not pos­sible to ‘see’ an object smal­ler than one wavelength of this light. In the vis­ible range, this wavelength is around 500 nanometres.

In quantum phys­ics, there is a prin­ciple called “wave-particle dual­ity”, accord­ing to which quantum objects (particles, atoms, etc.) exhib­it the beha­viour of both particles and waves. We can there­fore asso­ci­ate them with a wavelength, like light, and ima­gine a “mat­ter wave micro­scope”. The advant­age is that the wavelength asso­ci­ated with atoms is 1 mil­lion times short­er than that of light. We there­fore have a meas­ure­ment cap­ab­il­ity that is 1 mil­lion times bet­ter than that avail­able with light.

With quantum phys­ics, we have a meas­ure­ment cap­ab­il­ity that is 1 mil­lion times bet­ter than that avail­able with light.

Such devices do exist. They are known, for example, as « iner­tial sensors using atom­ic inter­fer­o­metry ». The fields of applic­a­tion are very broad, ran­ging from geosciences (detec­tion of oil slicks by meas­ur­ing vari­ations in the loc­al grav­ity field) to life sci­ences (meas­ure­ment of the elec­tric or mag­net­ic field emit­ted by a single cell) to iner­tial nav­ig­a­tion (on Earth or in space).

In 2022, an art­icle in Nature out­lined the pos­sib­il­ity of a grav­ity sensor of this type using the quantum beha­viour of free-fall­ing atoms to meas­ure micro­scop­ic vari­ations in the Earth’s grav­ity more accur­ately than ever before, in order to probe the struc­tures beneath the Earth’s surface.

The phar­ma­ceut­ic­al industry has also long since embraced quantum mechanics.

Medi­cines are molecules that bind to oth­er liv­ing struc­tures to provide health bene­fits for the patient. The way in which these molecules inter­act with each oth­er is stud­ied by a spe­cif­ic sci­entif­ic field called “quantum chemistry”.

Before a thera­peut­ic molecule is author­ised for the mar­ket, it must under­go a series of tests and clin­ic­al tri­als that rarely take less than a dec­ade. In order to tar­get molecules of interest very quickly, there is a stage called « vir­tu­al high-through­put screen­ing », where extremely com­plex algorithms test in par­al­lel the abil­ity of thou­sands of molecules to demon­strate the desired bio­chem­ic­al effect on the target.

This under­stand­ing of how an indi­vidu­al molecule chem­ic­ally binds to oth­er nano­met­ric struc­tures requires the devel­op­ment of digit­al sim­u­la­tion tools incor­por­at­ing all the prin­ciples of quantum mech­an­ics and chem­istry, with the aim of deliv­er­ing their res­ults as quickly as pos­sible, des­pite the colossal com­plex­ity of the cal­cu­la­tions involved.

In France, a start-up called Qbit phar­ma­ceut­ic­als is devel­op­ing new cal­cu­la­tion meth­ods com­bin­ing neur­al net­works, super­com­puters and quantum com­puters to tar­get the medi­cines of tomor­row ever more quickly and effect­ively⁴.