Quantum machine learning at LHCb: First proton-proton collisions at a world-record energy announced

With its brand-new detec­tor designed to han­dle sig­nif­i­cant­ly more chal­leng­ing data-tak­ing con­di­tions, the Quan­tum machine learn­ing (QML) at the Large Hadron Col­lid­er beau­ty (LHCb) exper­i­ment at Con­seil Européen pour la Recherche Nucléaire (CERN) recent­ly announced the first pro­ton-pro­ton col­li­sions at a world-record ener­gy.

The DPA team, led by Uni­ver­si­ty of Liv­er­pool senior research physi­cist Eduar­do Rodrigues, has demon­strat­ed for the first time the suc­cess­ful use of Quan­tum machine learn­ing tech­niques for the iden­ti­fi­ca­tion of the charge of b‑quark ini­ti­at­ed jets at the The Large Hadron Col­lid­er (LHC).

Quantum machine learning, quantum computing and their ‘interaction’

While machine-learn­ing algo­rithms are used to process enor­mous amounts of data, quan­tum machine learn­ing makes use of qubits, quan­tum oper­a­tions, or spe­cif­ic quan­tum sys­tems to boost the speed and accu­ra­cy of com­pu­ta­tion and data storage.

The quan­tum com­put­er pro­vides a com­plete­ly new type of com­put­ing hard­ware to the machine learn­ing hard­ware pool: quan­tum com­put­ers. The quan­tum the­o­ry explains the com­plete­ly dis­tinct phys­i­cal prin­ci­ples that sup­port infor­ma­tion pro­cess­ing on quan­tum computers.

On the oth­er hand, quan­tum com­put­ing is a way of com­put­ing that relies on the prin­ci­ples of quan­tum mechan­ics to func­tion. Data is encod­ed in bits, which can only be either 1 or 0, in tra­di­tion­al com­put­ing. On the oth­er hand, qubits, which can be both 1 and 0, are used in quan­tum computing.

Quan­tum machine learn­ing inves­ti­gates how con­cepts from quan­tum com­put­ing and machine learn­ing inter­act. The hard­ware we use to run our algo­rithms has always defined the lim­its of what com­put­ers can learn; for instance, par­al­lel graph­ics pro­cess­ing unit (GPU) clus­ters enable the suc­cess of mod­ern deep learn­ing with neur­al networks.

Mod­ern deep learn­ing algo­rithms are applied to large data sets, but the hard­ware lim­its the size of these data sets. To go beyond this lim­it, we need new approach­es that make use of quan­tum capabilities.

Application of quantum machine learning

Quan­tum machine learn­ing is a way for­ward for quan­tum com­put­ing and machine learn­ing research. It com­bines the best of both worlds: Quan­tum com­put­ers can solve cer­tain class­es of prob­lems in far less time than tra­di­tion­al com­put­ers, for exam­ple those relat­ed to opti­miza­tion or machine learn­ing. The the­o­ry behind quan­tum machine learn­ing is still under devel­op­ment, but the first suc­cess­es are being seen in prac­ti­cal applications.

For exam­ple, quan­tum machine learn­ing can help in improv­ing pat­tern recog­ni­tion, which in turn, will make it eas­i­er for sci­en­tists to pre­dict extreme weath­er events and poten­tial­ly save thou­sands of lives a year. Devel­op­ing a room-tem­per­a­ture super­con­duc­tor, elim­i­nat­ing car­bon diox­ide for a bet­ter envi­ron­ment, mak­ing sol­id-state bat­ter­ies, and enhanc­ing the nitro­gen-fix­a­tion process for the pro­duc­tion of ammo­nia-based fer­til­iz­er are some of the urgent prob­lems that could be solved with quan­tum computing.

This paper demon­strat­ed, for the first time, that Quan­tum machine learn­ing can be used with suc­cess in LHCb data analy­sis. — Dr. Eduar­do Rodrigues

More­over, quan­tum machine learn­ing will be cru­cial in devel­op­ing nov­el tech­nolo­gies. Quan­tum machine learn­ing can help us under­stand quan­tum effects and dis­cov­er appli­ca­tions for quan­tum com­put­ing. Anoth­er exam­ple is quan­tum cryp­tog­ra­phy, the abil­i­ty to try to hide infor­ma­tion from eaves­drop­pers, or quan­tum metrol­o­gy, the abil­i­ty to mea­sure and record the dis­tri­b­u­tion of mate­r­i­al prop­er­ties by using a quan­tum computer.

Last but not least, quan­tum machine learn­ing is used for devel­op­ing arti­fi­cial intel­li­gence (AI) algo­rithms that will ana­lyze huge amounts of data in a dif­fer­ent way than clas­si­cal ones.

The com­bi­na­tion of both fields will cer­tain­ly reshape soci­ety. It will change the way we live and think when com­bined with blockchain tech­nol­o­gy, which is also a com­bi­na­tion of dif­fer­ent sci­en­tif­ic fields, such as cryp­tog­ra­phy, dis­trib­uted sys­tems, and peer-to-peer networking.

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Our future depends on the con­ver­gence of tech­nolo­gies and their inte­gra­tion into our every­day lives. But let’s go back to quan­tum machine learn­ing and the lat­est exper­i­ment con­duct­ed by the Data Pro­cess­ing & Analy­sis (DPA) team of researchers.

Experiment by the DPA team

The DPA project is a major ren­o­va­tion of the offline analy­sis frame­work to allow full exploita­tion of the sig­nif­i­cant increase in data flow from the upgrad­ed LHCb detector.

For the medi­um and longer term, this effort is a part of R&D beyond the just-start­ing new data tak­ing period.

In LHCb analy­sis, the usage of machine learn­ing tech­niques is com­mon. Giv­en the quick devel­op­ment of quan­tum com­put­ing and quan­tum tech­nolo­gies, it seems sen­si­ble to start look­ing into whether and how quan­tum algo­rithms can func­tion on this new hard­ware, as well as whether or not the LHCb par­ti­cle physics use-cas­es may prof­it from the grow­ing field of quan­tum computing.

The team used QML tech­niques for the first time to deal with the task of hadron­ic jet charge iden­ti­fi­ca­tion. Till now, QML tech­niques have most­ly been used in par­ti­cle physics to solve event clas­si­fi­ca­tion and par­ti­cle track recon­struc­tion challenges.

Based on a sam­ple of sim­u­lat­ed b‑quark ini­ti­at­ed jets, the study “Quan­tum Machine Learn­ing for b‑jet charge iden­ti­fi­ca­tion” was accom­plished. A Deep Neur­al Net­work (DNN), a mod­ern, pow­er­ful type of con­ven­tion­al (i.e., non-quan­tum) arti­fi­cial intel­li­gence algo­rithm, was used to com­pare the per­for­mance of a so-called Vari­a­tion­al Quan­tum Clas­si­fi­er that is based on two dif­fer­ent quan­tum cir­cuits. Although tests on actu­al hard­ware are now being devel­oped, the per­for­mance is exam­ined using a quan­tum sim­u­la­tor because the quan­tum hard­ware that is cur­rent­ly on the mar­ket is still in its ear­ly stages.


The DNN worked mar­gin­al­ly bet­ter than the quan­tum machine learn­ing algo­rithms when the results were com­pared to those pro­duced using a clas­si­cal Deep Neur­al Network.

The study shows that the quan­tum method of machine learn­ing achieves max­i­mum per­for­mance with min­i­mal events. As a result, it assists in low­er­ing resource uti­liza­tion, which will become vital at LHCb giv­en the vol­ume of data obtained in com­ing years. How­ev­er, the DNN sur­pass­es Quan­tum meth­ods for machine learn­ing when more fea­tures are used. With the avail­abil­i­ty of more effec­tive quan­tum hard­ware, improve­ments are expected.

Quan­tum algo­rithms can be used to study cor­re­la­tions between fea­tures, accord­ing to research con­duct­ed in part­ner­ship with sub­ject mat­ter experts. This would allow it to gath­er data on cor­re­la­tions between jet con­stituents, which would enhance the accu­ra­cy of iden­ti­fy­ing jet fla­vors.

“This paper demon­strat­ed, for the first time, that Quan­tum machine learn­ing can be used with suc­cess in LHCb data analy­sis”, Dr. Eduar­do Rodrigues said. Quan­tum machine learn­ing is just begin­ning to be used in par­ti­cle physics exper­i­ments. Because of the wide­spread inter­est and invest­ment in quan­tum com­put­ing, sig­nif­i­cant advances in hard­ware and com­put­er tech­nolo­gies are to be expect­ed as sci­en­tists devel­op expe­ri­ence with it.

“This work, which is part of the R&D activ­i­ties of the LHCb DPA project, pro­vid­ed valu­able insight into Quan­tum machine learn­ing. The inter­est­ing (first) results open new avenues for clas­si­fi­ca­tion prob­lems in par­ti­cle physics exper­i­ments”, Dr. Rodrigues added.

Future implications of the findings

From the study, it is obvi­ous that the DNN has a bet­ter per­for­mance than the clas­si­cal machine learn­ing algo­rithms when the results were com­pared to those pro­duced using a con­ven­tion­al Deep Neur­al Network.

The study found that sig­nif­i­cant per­for­mance gains can be obtained for the DNN algo­rithms, which could have direct impli­ca­tions on future events analy­sis and recon­struc­tion at LHCb.

In the future, improve­ments to the hard­ware could lead to even more impres­sive per­for­mance. The next step could be to test the per­for­mance of these meth­ods on actu­al data of real b‑quark jets at LHCb.

More­over, this find­ing will enable the imme­di­ate imple­men­ta­tion of Quan­tum machine learn­ing tech­niques into the analy­sis of real LHCb data. Researchers believe that Quan­tum machine learn­ing will sig­nif­i­cant­ly boost the over­all per­for­mance of the LHCb exper­i­ment, pro­vid­ing vital infor­ma­tion for a deep­er under­stand­ing of physics beyond the Stan­dard Mod­el and ulti­mate­ly new discoveries.

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