1、2022/9/201量子計(jì)算研究進(jìn)展彭新華中國(guó)科學(xué)技術(shù)大學(xué)近代物理系2010. 3. 262022/9/202量子信息“Information is physical”. - Rolf Landauer 量子計(jì)算機(jī)：基于量子力學(xué)原理，存儲(chǔ)、 處理量子信息的計(jì)算裝置。 量子計(jì)算量子通訊量子密碼學(xué)交叉領(lǐng)域量子物理信息科學(xué)計(jì)算機(jī)科學(xué)量子信息2022/9/203內(nèi)容提綱量子計(jì)算發(fā)展簡(jiǎn)介磁共振量子計(jì)算研究進(jìn)展 未來(lái)研究方向2022/9/204一、量子計(jì)算發(fā)展簡(jiǎn)介2022/9/205計(jì)算機(jī)硬件歷史計(jì)算機(jī)硬件是信息處理的平臺(tái)。 數(shù)值計(jì)算單元: 機(jī)械齒輪/電子機(jī)械傳動(dòng)裝置電子管 (1911 - 1946)晶體

2、管 (1947 - 1958)集成電路 (1959 - 1970)大規(guī)模集成電路 (1971 - )2022/9/206 計(jì)算機(jī)歷史2022/9/2071642, Pascal帕斯卡機(jī)械計(jì)算機(jī)，首次確立了計(jì)算機(jī)器的概念。概念1834, Babbage差分機(jī)提出了分析機(jī)的概念機(jī)械裝置2022/9/208世界上第一臺(tái)電子計(jì)算機(jī)-1946 ENIACMauchiy and Eckert2022/9/209ENIAC2022/9/20101952, EDVACVon NeumannElectronic Discrete Variable Automatic ComputerContaining 230

3、0 vacuum tubes, but 10 times faster than ENIAC (18000)2022/9/2011微處理器1971 Intel 400410um, 2300晶體管0.74 MHz1978 Intel 80863um, 29000 晶體管4.77MHz2008, Core i745nm, 5.82 billion晶體管2.66 - 3.2 GHz2022/9/20122022/9/2013摩爾定理2022/9/20142022/9/2015Getting Smaller Size of Atom2022/9/20162022/9/20172022/9/2018當(dāng)今

4、微電子技術(shù)不久將面臨物理極限！高速發(fā)展 vs. 物理極限！熱耗散 & 量子效應(yīng)科學(xué)技術(shù)發(fā)展趨勢(shì)、國(guó)家重大戰(zhàn)略需求 開(kāi)辟全新的信息處理方式，發(fā)展以量子比特為基礎(chǔ)的量子信息處理技術(shù)。2022/9/2019量子計(jì)算機(jī)的發(fā)展史In the 1970s Fredkin, Toffoli, Bennett and others began to look into the possibility of reversible computation to avoid power loss.Since quantum mechanics is reversible, a possible link betwe

5、en computing and quantum devices was suggestedSome early work on quantum computation occurred in the 80s1982 Benioff: Quantum computers are universal.1982 Feynman: Quantum computer could simulate other quantum systems.1993 Bernstein, Vazirani and Yao: Quantum systems are more powerful than classical

6、 computers.2022/9/2020量子計(jì)算機(jī)的發(fā)展史Quantum algorithms1985 Deutsh: the first quantum algorithm1994 Coppersmith, Shor: quantum fourier transform, factorization1997 Grover: a unsorted quantum search algorithmImplementations1995 Monroe, Meekhof, King, Itano, Wineland: CNOT gate implemented in ion trap by NI

7、ST1997 Gershenfeld, Chuang, Cory, Fahmy, Havel: NMR quantum computing2001 Vandersypen et al. : Experimental realization of Shors algorithm2006: Negrevergne et al. Benchmarking quantum control on a 12-qubit system.2022/9/2021量子比特sNatural qubits:Spin 1/22022/9/2022量子態(tài)疊加原理2022/9/2023可逆邏輯們可逆邏輯們 克服熱耗散問(wèn)題封

8、閉的量子系統(tǒng)按照哈密頓量做幺正演化，本身就是可逆操作。Classical GateInOutGateInOutQuantum 2022/9/2024Classical vs. QuantumClassical bits transistors 0 or 1Quantum bits quantum systems 0 or 1or in-betweenNAND, NOT, AND NAND, NOT, CNOT Sqrt(NOT) These quantum gates allow operations that are impossible on classical computers!202

9、2/9/2025量子信息特點(diǎn)高速計(jì)算大容量信息 存儲(chǔ)、傳輸保密通信量子態(tài)疊加原理量子糾纏性量子態(tài)不可克隆定理量子物理 原理支配下 的信息處理1 0Bit 0 or 1 in computer now2022/9/2026大數(shù)質(zhì)因子分解Problem: Given a l-bit integer N=pxq，to find its nontrivial prime factors p and q？ N = ? x ?Best-known classical Algorithms:in sub-exponential time!Shors algorithm:In polynomial time!

10、The presumed difficulty of this problem is at the heart of certain algorithms in cryptography such as RSA.2. P.Shor, in Proc. 35th Annu. Symp. on the Foundations of Computer Science, (IEEE Computer Society Press, Los Alamitos, California, 1994), p. 124-134.1. M.A. Nielsen and I.L. Chuang, Quantum Co

11、mputation and Quantum Information. Cambridge University Press, Cambridge, 2000.2022/9/2027Time required: Classical vs. quantum2.5 days42 days19000 yearsHalf a yearAge of universe2022/9/2028The promise of Quantum ComputationSearching databases1 unsorted list of N entries how many queries? 1 month27 m

12、inutesFactoring Integers2 N = pq N has L digits given N, what are p and q? 19000 years42 days1000 digits1 L.K. Grover, PRL, 79, 4709 (1997) 2 P. Shor, Proc. 35th Ann. Symp. On Found. Of Comp. Sci., p.124 (1994)2022/9/2029二、磁共振量子計(jì)算研究進(jìn)展2022/9/2030DiVincenzo判據(jù):1. 可擴(kuò)展的具有良好特性的量子比特系統(tǒng)。2. 能夠制備量子比特到某個(gè)基準(zhǔn)態(tài)。3.

13、能夠保持足夠長(zhǎng)的相干時(shí)間來(lái)完成各種 量子邏輯門(mén)操作。4. 能夠?qū)崿F(xiàn)一套通用量子邏輯門(mén)操作。5. 能夠?qū)崿F(xiàn)對(duì)量子比特的測(cè)量。量子計(jì)算機(jī)的物理實(shí)現(xiàn)1 DiVincenzo D.P., Fortschr. Physik, 48 (9-11), 771 783 (2000)(1)能長(zhǎng)期保持相干性與外界很好隔離的封閉量子系統(tǒng)(2)外界能夠精確地控制其演化并讀出結(jié)果與外界有良好的耦合這兩個(gè)要求互相矛盾。因此選擇什么樣的物理體系來(lái)制作量子計(jì)算機(jī)要兼顧兩者的要求。一臺(tái)量子計(jì)算機(jī)最基本要求實(shí)驗(yàn)物理體系相對(duì)于經(jīng)典計(jì)算機(jī)利用了電子的電荷特性，在量子計(jì)算的研究中，利用電子的自旋特性，結(jié)合電子自旋操作迅速和核自旋相干時(shí)

14、間長(zhǎng)的特點(diǎn)，開(kāi)展磁共振量子計(jì)算是量子計(jì)算機(jī)研究重要發(fā)展方向之一。系統(tǒng)相干時(shí)間/秒操作時(shí)間/秒最大運(yùn)算次數(shù)目前進(jìn)展/比特?cái)?shù)電子自旋10- 10-10- 10-1032核自旋10-1010- 10-10312離子阱10-110-1410138（3）量子點(diǎn)10-610-91032光學(xué)腔10-510-141092微波共振腔10010-41042一些物理體系的比較2022/9/2034一些物理體系的比較Benchmarking values: approximate error rates for single or multi-qubit gates.2022/9/2035核自旋量子位B0Spin p

15、article in magnetic field:|0|11 Gershenfeld, N. et al., Science, 275, 350 356 (1997) 2 Cory D. et al., Proc. Natl. Acad. Sci., 94, 1634 1639 (1997)2022/9/2036實(shí)驗(yàn)原理：儀器NMR量子計(jì)算機(jī)控制：射頻磁場(chǎng) + 核之間的相互作用 實(shí)驗(yàn)平臺(tái)2022/9/20382.1 絕熱量子計(jì)算背景：傳統(tǒng)的量子計(jì)算研究中，研究者將經(jīng)典計(jì)算機(jī)模型類比到量子情形，以期通過(guò)基本邏輯操作實(shí)現(xiàn)普適量子計(jì)算。優(yōu)點(diǎn)：適用于廣泛的組合優(yōu)化問(wèn)題，有著重要的應(yīng)用前景。比傳統(tǒng)的量

16、子計(jì)算機(jī)具有更強(qiáng)的容錯(cuò)能力。絕熱量子計(jì)算：MIT的Farhi等人在2001年提出的一種新的量子計(jì)算途徑。E. Farhi et.al., Science 292，472 (2001) 2022/9/20392.1 絕熱量子計(jì)算Schrdinger equation:Adiabatic evolutionEncoding the solution of the problem123Linear interpolationEasy to find2022/9/20402.1 新的質(zhì)因子分解的絕熱量子算法分解21需要3個(gè)量子比特我們的算法Shor算法分解21需要50毫秒XH Peng et al.,

17、 Phys. Rev. Lett. 101, 220405 (2008)Shors algorithm for 15: 7 qubits; 720msOur new adiabatic algorithm for 21: 3 qubits; 50ms2022/9/20412.2 模擬量子系統(tǒng)Classical computersExponential growth of Hilbert spaceSystem with 50 qubits250 1015 complex amplitudes 32 x 1015 bytes of informationwell beyond the capac

18、ity of existing computersIs it possible to classically simulate faithfully a quantum system?Nave answer: NOncomputational basis2022/9/2042Quantum computers Universal quantum simulators1982 Richard P. Feynmann R.P. Feynman, “Simulating Physics with Computers”, Int. J. Theor. Phys. 21, 467-488, 1982Ca

19、n we do it with a new kind of computer a quantum computer? Now it turns out, as far as I can tell, that you can simulate this with a quantum system, with quantum computer elements. I therefore believe its true that with a suitable class of quantum machines you can imitate any quantum system, includi

20、ng the physical world. 4.2 模擬量子系統(tǒng)2022/9/20432.2.1 量子仿真實(shí)驗(yàn)研究背景量子相變與臨界現(xiàn)象是凝聚態(tài)物理學(xué)中重要物理現(xiàn)象；量子自旋系統(tǒng)聯(lián)系著量子信息學(xué)和凝聚態(tài)物理兩個(gè)領(lǐng)域；量子糾纏和量子相變的密切關(guān)系。研究結(jié)果設(shè)計(jì)合適的Hamiltonian微擾和掃描函數(shù)實(shí)現(xiàn)量子絕熱過(guò)程；首次成功地觀察到了Heisenberg自旋鏈中基態(tài)糾纏的量子相變現(xiàn)象。XH Peng et al., Physical Review A 71, 012307 (2005) Much more susceptible to the change of the controlled

21、 parameter2022/9/20442.2.2 量子仿真實(shí)驗(yàn)Loschmidt echo or Fidelity decay:LE = |2A visualization of “quantum fluctuations”研究結(jié)果JF Zhang, XH Peng et al., Phys. Rev. Lett. 100, 100501 (2008)2022/9/20452.2.3 量子仿真實(shí)驗(yàn)三體相互作用體系中量子相變與量子糾纏的實(shí)驗(yàn)研究基態(tài)臨界點(diǎn)探測(cè)問(wèn)題：標(biāo)準(zhǔn)兩自旋相關(guān)函數(shù)不能探測(cè)由于三體相互作用導(dǎo)致的量子臨界現(xiàn)象。2022/9/2046Three-spin Ising quantu

22、m model2.2.3 量子仿真實(shí)驗(yàn)Phase IPhase IIIIAIBICVisible by entanglement witnessesXH Peng et al., Phys. Rev. Lett. 101, 140501 (2009)量子仿真計(jì)算氫分子基態(tài)能量J. Du et al. PRL. 104，030501 (2010) 2010年，首次在實(shí)驗(yàn)上通過(guò)磁共振技術(shù)實(shí)現(xiàn)了氫分子的基態(tài)能量值計(jì)算的量子仿真研究。2.2.4 量子仿真實(shí)驗(yàn) 該工作被選為Phy. Rev. Lett. Highlight Article。2.2.4 量子仿真實(shí)驗(yàn)2022/9/20492.3 規(guī)?；c消

23、相干2022/9/2050 固態(tài)體系中最優(yōu)動(dòng)力學(xué)去耦實(shí)驗(yàn)J. Du et al. Nature 461, 1265 (2009)2009年，首次在真實(shí)固態(tài)體系中實(shí)現(xiàn)了最優(yōu)動(dòng)力學(xué)去耦，極大的提高了量子相干保存時(shí)間。2.3 規(guī)?；c消相干發(fā)展高速、精確的量子操控技術(shù) 新型量子信息存儲(chǔ)載體的研究絕熱量子計(jì)算和量子仿真研究抗噪聲量子方法的探索：退相干機(jī)理及抑制方法研究三、未來(lái)研究方向542022/9/2055結(jié)語(yǔ)從量子計(jì)算（機(jī)）的概念提出以來(lái)，此領(lǐng)域的研究進(jìn)展已經(jīng)表明：這種新型量子處理器具有比經(jīng)典處理器更強(qiáng)的信息處理功能。研究量子計(jì)算與量子計(jì)算機(jī)是社會(huì)經(jīng)濟(jì)與科技發(fā)展提出的迫切需求，同時(shí)也會(huì)推動(dòng)納米技術(shù)和微觀操控等高新技術(shù)的進(jìn)步，是未來(lái)信息技術(shù)發(fā)展的重要戰(zhàn)略性方向。量子計(jì)算的實(shí)現(xiàn)已不存在原理性障礙，量子計(jì)算非常脆弱，使制造規(guī)模大的量子計(jì)算機(jī)變得十分困難，這是對(duì)人類智慧和能力的挑戰(zhàn)！ 量子計(jì)算機(jī)的研制不管成功與否，量子計(jì)算的研究一定會(huì)給人類未來(lái)的生活帶來(lái)深遠(yuǎn)意義的影響。路漫漫其修遠(yuǎn)兮，吾將上下而求索！2022/9/20565