AN KAMA SAUTI YANA TSALLE, QUANTUM ƊAYA BAYAN ƊAYA

Ka kaɗa igiyar garaya (guitar) kuma sautin yana mutuwa a hankali. Kimiyyar quantum mechanics, duk da haka, tana hasashen cewa ƙarfin kowane abu mai girgiza yana zuwa cikin ƙunshi daban-daban — phonon, quanta na sauti. Matsalar ita ce ba za ka iya ganin su ta kallon motsin abun ba. Auna matsayi koyaushe yana nuna raguwa mai santsi ta exponential kawai, daidai kamar oscillator na gargajiya.

Don bayyana ƙunshin, dole ne ka auna ƙarfin kansa, kuma ka yi hakan ba tare da ka dagula shi ba: abin da ake kira auna quantum mara rushewa (quantum non-demolition measurement). An fara ganin irin waɗannan tsalle-tsalle tsakanin matakan ƙarfi a cikin ions ɗaya-ɗaya da aka kama, sannan ga ƙwayoyin haske da aka kama a cikin cavity. Wata tawaga a Jami’ar Stanford da SLAC, ƙarƙashin jagorancin Amir Safavi-Naeini, yanzu ta yi hakan ga abu mai girgiza.

Crystal da ke shawagi sama da qubit

Abu mai girgizar shi ne wani ƙaramin dunƙule na lithium niobate, wani crystal da ke mayar da girgiza zuwa wutar lantarki (voltage). Yana zaune a tsakiyar wani katako mai zane wanda ramukansa masu maimaitawa ke aiki a matsayin madubai na sauti, suna kama girgizar a ciki. Nauyinsa na tasiri kusan picogram 0.2 ne — kashi ɗaya bisa biyar na kashi ɗaya cikin tiriliyan na gram.

Mai ganowa shi ne superconducting qubit, irin da’irar da ake amfani da ita a kwamfutocin quantum. Ana ƙera sassan biyu daban, sannan wata na’urar haɗawa mai daidaito tana buga crystal ɗin a kan qubit, ta yadda dunƙulen yana shawagi kawai nanometre 75 sama da shi.

Haɗin yana aiki kamar haka: kowane phonon a cikin dunƙulen yana sauya mitar qubit da kilohertz 328. Ta hanyar daidaita lokacin wani gajeren jerin bugun (pulse sequence), qubit ɗin yana ƙarewa a wani yanayi idan adadin phonon ɗin ya kasance cikakke (even) kuma a ɗayan idan ya kasance mara cikakke (odd). Tunda dunƙulen ba ya riƙe fiye da phonon ɗaya a aikace, wannan ya zama tambaya mai sauƙi: sifili ko ɗaya? Kowace dubawa tana ɗaukar kusan microsecond 12.

Tsalle-tsallen

Da farko, tawagar ta koyi gane phonon ɗaya. Dubawa ɗaya tana daidai kusan kashi 68% na lokaci kawai, don haka suna maimaita ta: bayan amsoshi shida na “phonon ɗaya” a jere, dunƙulen yana riƙe daidai phonon ɗaya da yiwuwa ta kashi 85%.

Sannan sun ci gaba da tambaya — sau 294 a jere. Amsoshin danye sun riga sun nuna shi a ido: doguwar tazara ta galibi “ɗaya”, sannan sauyi kwatsam zuwa galibi “sifili”. Dunƙulen bai zubar da ƙarfinsa a hankali ba; ya rasa phonon ɗinsa ɗaya a tsalle ɗaya, a wani lokaci na bazuwar da ya bambanta daga wani gudu zuwa na gaba. Lokutan waɗannan tsalle-tsalle suna bin dokar exponential, alamar tsari na kai-tsaye mara ƙwaƙwalwa.

Lambobin da suka sa ya yiwu

Phonon yana rayuwa milisekan 2.1 a cikin wannan dunƙulen, abin da marubutan suka kira tsawo na musamman ga irin wannan resonator a mitocin gigahertz. Suna danganta hakan ga zaɓuɓɓuka biyu: babu ƙarfe da ke taɓa resonator ɗin, kuma ba a taɓa buga samansa da hasken ion da ake amfani da shi don sassaƙa shi ba.
Hakan yana bar wuri ga kusan dubawa 170 a cikin tsawon rayuwar phonon ɗaya.
Kowace dubawa tana barin phonon ɗin lafiya kusan kashi 99% na lokaci. Ƙaramin dagulawar yana rage rayuwar phonon ɗin zuwa kusan milisekan 0.65 yayin da ake kallonsa.
Ma’aunin inganci na haɗin gwiwa, da ake kira cooperativity, ya wuce miliyan 3, abin da marubutan suka bayyana a matsayin ninki goma fiye da sauran dandamalin acoustic na quantum.

Zuwa bits na quantum da aka yi da sauti

Mataki na gaba na marubutan shi ne bit na quantum mai “layi biyu” (dual-rail) da aka yi da resonator na inji biyu masu raba qubit ɗaya, inda rasa phonon ya zama kuskure da za a iya ganowa. Dabarar bugawarsu tana ba da damar resonator da yawa a kan chip ɗaya. Suna kuma nuna na’urorin ji (sensors): abu mai wannan sauƙin nauyi, mai girgiza na wannan tsawon lokaci, shi ne abin da auna nauyin ƙwayar halitta ɗaya (molecule) ke buƙata.

A yanzu, auna har yanzu yana da iyakoki: dubawa ɗaya tana nesa da cikakke, kuma ba za ta iya bambance phonon sifili da biyu ba. Biyu daga cikin marubutan Amazon Scholars ne, kuma Amazon Web Services ta taimaka wajen ɗaukar nauyin aikin.

Yanzu an ga tsalle-tsallen quantum a cikin atom, a cikin haske kuma, da wannan gwaji, a cikin sauti.