Lidar Mai Ƙarfafa Kwantum: Tsayayyar Auna Nisa Daga Garkuwar Al'ada

2.1 Iyakokin Lidar na Al'ada

Lidar na gani na al'ada, duk da cewa yana da mahimmanci don auna nisa daidai, yana fuskantar wahala a cikin yanayin ƙarancin sigina, babban bayanan baya. Lokacin da nunin hasken manufa ya yi ƙasa ko hayaniyar muhalli/garkuwa ta yi girma, tsarin al'ada ba zai iya bambanta hasken sigina daga hasken hayaniya da aminci ba, wanda ke haifar da raguwar rabon sigina-zuwa-hayaniya (SNR) da gazawar ganowar manufa.

2.2 Ka'idojin Haskakawa na Kwantum

Haskakawa mai ƙarfafa kwantum yana ba da mafita ta hanyar amfani da alaƙar haske mara al'ada. Ta amfani da tushen nau'i-nau'i na haske masu ba da sanarwa (misali, daga raguwar ƙididdiga ta atomatik), ana ajiye haske ɗaya ("mai jinkiri") a cikin gida a matsayin ma'auni, yayin da abokin haɗin gwiwarsa ("sigina") ake aika don bincika manufa. Ganowa tare da haɗin kai tsakanin sigina mai dawowa da mai jinkiri yana ba da ingantacciyar hanyar kin hayaniyar bayanan baya marasa alaƙa, domin hasken hayaniya ba zai yiwu ya zo daidai da lokacin sanarwar ba.

3.1 Tsarin Gwaji

Tsarin ya dogara ne akan tushen nau'i-nau'i na haske mai bugawa ci gaba (CW). Ana tura hasken sigina zuwa manufa, yayin da ake jinkirta mai jinkiri kuma a yi amfani da shi azaman mai ba da sanarwa. Masu ganowa haske guda ɗaya suna ɗaukar tashoshi biyu, kuma na'urar ƙididdiga ta haske guda ɗaya mai alaƙa da lokaci (TCSPC) tana rikodin abubuwan ganowa don binciken haɗin kai.

3.2 Tsarin Bincike na Log-Likelihood

Ana siffanta aiki ta amfani da gwajin rabon log-likelihood (LLR), hanyar ƙididdiga mafi kyau don bambance tsakanin hasashe biyu (manufa tana nan vs. babu) a ƙarƙashin hayaniya. Ana ƙididdige LLR, $\Lambda$, daga ƙididdigar haɗin kai da ƙididdiga guda ɗaya a kan lokacin bin $\Delta\tau$:

$\Lambda = \log\left(\frac{P(\text{bayani} | H_1)}{P(\text{bayani} | H_0)}\right)$

inda $H_1$ shine hasashen manufa tana nan kuma $H_0$ shine hasashen manufa ba ta nan. Wannan tsarin yana ba da ma'auni mai ƙarfi don amincewar ganowa da yuwuwar kuskure.

3.3 Ka'idar Bin Diddigin Bayanan Baya Mai Sauyi

An gabatar da sabuwar ka'idar don sarrafa matakan bayanan baya daban-daban. Tana kimanta ƙimar haɗin kai na bayanan baya a cikin ainihin lokaci ta hanyar nazarin lokutan bin inda ba a tsammanin ainihin haɗin kai na sigina ba (misali, a wajen tazarar lokacin dawowa da ake tsammani). Wannan yana ba da damar tsarin ya daidaita da sannu-sannun canje-canje a cikin hasken muhalli ko garkuwar ƙarancin mitar ba tare da ya lalata kin sa na saurin garkuwar sigina mai bugun jini ba.

4.1 Aikin Sigina-zuwa-Bayanan Baya

Tsarin ya yi nasarar gano manufa tare da yuwuwar dawowa (nunin haske) har ƙasa da -52 dB. Ya yi aiki da aminci ko da lokacin da ƙwararar hasken bayanan baya ta fi ƙwararar sigina fiye da matakan oda biyar (sau 100,000). Wannan yayi daidai da ƙarfafa kwantum na kusan 30 dB a cikin ma'aunin kuskure idan aka kwatanta da mafi kyawun tushen haske mai daidaituwa na al'ada a ƙarƙashin irin wannan yanayin, ko rage lokacin da ake buƙata don samun ƙaramin yuwuwar kuskure sau 17.

4.2 Gwaje-gwajen Tsayayya da Garkuwa

Tsarin ya nuna kariya daga duka garkuwar sauri (mai bugun jini) da juriya ga garkuwar sannu-sannu (karkata). Ka'idar bin diddigin bayanan baya mai sauyi ta cire sannu-sannun ɓangaren yadda ya kamata, yana hana kuskuren faɗakarwa ko rasa ganowa, yayin da ƙofar haɗin kai ta asali ta ki amincewa da hayaniyar bugun jini mai girma.

4.3 Daidaiton Auna Nisa

Da aka tsawaita tsarin zuwa auna nisa mai aiki, marubutan sun gano wurin manufa tare da ƙayyadaddun sararin samaniya na 11 cm. Wannan ƙayyadaddun ya kasance an iyakance shi da asali ta hanyar girgizar lokaci na masu ganowa haske guda ɗaya, ba ta hanyar ka'idar kwantum kanta ba, wanda ke nuna yuwuwar ingantawa tare da mafi kyawun masu ganowa.

5.1 Cikakkiyar Fahimta

Wannan ba wani ƙarin nunin dakin gwaji ne kawai ba. Mrozowski da sauransu sun ba da darasi mai zurfi a cikin injiniyanci na kwantum mai aiki. Sun kauce wa rikicin bin cikakkiyar fa'idar jihar Gaussian na 6 dB—wata manufa da, kamar yadda aka lura a cikin ayyukan daga Laboratory na Kwantum Photonics na MIT, ya ci gaba da cike da rikitarwa na mafi kyawun ma'auni—a maimakon haka sun gina tsarin da ke amfani da ingantattun alaƙar lokaci masu fahimta daga SPDC mai bugawa CW. Gaskiyar hazaka ita ce mayar da hankali a kan tsayayya da garkuwa, yana motsa hankalin kwantum daga wani abu mai ban sha'awa na "dakin shiru" zuwa fasaha da ke magance matsanancin yanayin gazawar tsarin al'ada a duniyar gaske.

5.2 Tsarin Ma'ana

Ma'anar takardar tana da gamsarwa: (1) Gano ƙashin ƙafar lidar na al'ada (hayaniya/garkuwa). (2) Karɓi hanyar kwantum (haske masu ba da sanarwa) waɗanda ke tace hayaniya ta hanyar haɗin kai. (3) Amincewa da iyakan aiki (sannu-sannun karkatar bayanan baya na iya kwaikwayon sigina) kuma ƙirƙiri gyaran software (bin diddigin bayanan baya mai sauyi). (4) Tabbatar da tsarin haɗin gwiwa a ƙarƙashin matsanancin yanayi, masu dacewa da soja (babban hayaniya, ƙarancin sigina, garkuwa mai aiki). Wannan tsarin warware matsaloli har zuwa ƙarshe shine abin da ke raba ƙwaƙƙwaran samfuri daga aikin ilimi.

5.3 Ƙarfafawa & Kurakurai

Ƙarfafawa: Mahimmanci na -52 dB da kin bayanan baya 10⁵:1 nasarori ne masu ƙima. Ka'idar bin diddigin mai sauyi sabon abu ne mai wayo, mara nauyi wanda ke haɓaka aikin gaske. Amfani da tushen CW yana sauƙaƙa gine-ginen idan aka kwatanta da tsarin bugun jini, yana inganta kwanciyar hankali da yuwuwar ƙanƙanta.
Kurakurai & Tambayoyi: Ƙayyadaddun 11 cm, duk da yana da kyau, an iyakance shi da mai ganowa. Ta yaya wannan ke haɓaka tare da nisa? Takardar ba ta yi magana game da iyakar aikin tsarin ba, wani muhimmin ma'auni. Bugu da ƙari, haske da kaddarorin haske na tushen nau'i-nau'i na haske za su ƙayyade ƙimar sabuntawa da ɓoyewa—ma'auni masu mahimmanci don turawa. Kwatancin da "al'ada" an bayyana shi da kyau amma bai magance ci-gaban fasahohin al'ada kamar tacewa ta lokaci mai daidaitawa ko ingantaccen gyara ba, waɗanda suke gasa ta gaske.

5.4 Fahimta Mai Amfani

Ga masu saka hannun jari da manajoji na R&D: Mayar da hankali kan labarin haɗin kai da tsayayya, ba kawai lambar fa'idar kwantum ba. Wannan aikin ya tabbatar da cewa fa'idar kusa da lokaci na lidar na kwantum yana cikin muhallin da aka hana. Hanyar ci gaba ta nan take a bayyane: 1) Haɗa masu ganowa haske guda ɗaya na superconducting nanowire (SNSPDs) masu ƙarancin girgiza don tura ƙayyadaddun ƙasa da 5 cm. 2) Haɓaka ƙananan, hasashe masu haske masu haɗin kai, bin jagorancin kamfanoni kamar PsiQuantum da Xanadu a cikin lissafin kwantum na hoto. 3) Haɗin gwiwa tare da kwangilolin tsaro/sararin samaniya (misali, Lockheed Martin's Skunk Works, BAE Systems) don gwajin filin a cikin yanayin garkuwa da ɓarna na gaske. Gasar ba ta ƙara game da tabbatar da ka'ida a cikin takarda ba, amma game da ƙarfafa ta don filin.