这项研究是由卓越的澳大利亚研究理事会中心的量子计算和通讯技术，项目编号CE110001027支持。

1。一些定制的元素<ol><li> 环谐振器 在该实验中，两个环形谐振器进行分割，并结合不同频率的光束是必需的。腔的设计示于图。 2。 <ol><li>围绕散装铝中空圆柱体谐振器。在一端，安装两个平面镜具有相同的反射率。在另一端安装一个最大反射曲面镜。镜不需要粘在谐振器隔离。与隔板的精心加工时，端帽都足以将它们保持在到位。 </li><li>结合曲面镜有一O形环和压电致动器，以允许所述腔的谐振频率的控制。放置反射镜和谐振器隔离之间的O形圈，与反射镜后面的压电。压缩这些元素放到谐振器隔离与端帽，以允许端镜的快速致动。 O型圈的压缩相结合和高速压电通常允许超过10 kHz的控制带宽。 注意：在这个例子中，该隔离层是约25厘米长。此长度是任意的，但应选择这样的控制和探测光不coresonant，这意味着超精细分裂不能自由光谱范围的倍数。由于该环的几何形状，腔体将具有不同的精细度的非简并偏振模式。定制涂覆镜被指定，以提供精细度的空腔周围千对s偏振光，从而导致大约100对p-偏振光的技巧。虽然这些实验在低精细度模式，通常进行的，安装可以很容易地切换到高技巧模式应要求的光束更强的过滤。 </li></ol></li><li> 存储单元，其外壳设计 <ol><li>要构建存储设备，使用含有同位素提高87 Rb的人长的电池翁以0.5托的氪缓冲气体。在设置时，长度为20cm。小区的窗户是防反射涂层。该细胞必须在使用非磁性加热丝被加热到80℃左右。 </li><li>包住细胞在三个同心螺线管。两个内螺线管创建的磁场梯度。风这些电磁阀，执行用毕奥 - 萨伐尔公式模拟。模拟的可变螺距的螺线管，将提供一个线性变化的磁场。 </li><li>使用图形程序，打印出这个螺旋的情节到一张纸上。环绕PVC管的文件，以提供一条线跟踪和缠绕电线到管道上。 注意：在此设置的线圈是长50厘米，气室过两次的长度，以避免边缘效应。直径是6和10厘米，这是两倍的小区的直径，以确保磁场大多是纵向。梯度线圈彼此面对这样的临屋区它们之间吨切换将切换渐变的符号（ 见图3）。在一个典型的实验中，电流2-3 A到这些线圈运行和线圈切换在3-4微秒。 </li><li>为了优化开关时间和振荡停止使用200Ω阻尼电阻器串联的线圈。将这些两个螺线管，是用来提供一个直流磁场解除塞曼级简并的第三个通常的线绕线圈的内侧。铷具有大约1.4兆赫磁场26 / G的变化。一个典型的直流场是6 G，而梯度将2克/米。 </li><li>放置μ-金属屏蔽两层围绕三个磁线圈以降低地球磁场对实验的影响。 </li></ol></li></ol> 2。光学光路布局 <ol><li>使用单模激光器调谐铷日1线在795 nm处附近。监测频率使用饱和吸收测量， 如图3中的激光的。由约1.5千兆赫以上的F = 2到F&#39;= 2跃迁失谐频率。这将是控制光束的近似频率。 </li><li>在分束器BS2，挖掘一些灯灭主激光形成控制光束。通过使用声光调制器AOM1改变其频率。该AOM还允许控制光束的功率调制。以驱动AOM，通过由一个TTL信号来控制的RF开关传递一个信号源的输出端，然后把它发送到AOM之前放大信号。微调控制频率，以优化的拉曼吸收，例如，通过改变这AOM的驱动频率。该声光调制器中的设置的射频驱动频率为80MHz，但是这是任意的。 </li><li>失谐的探测光束，将被存储在量子存储器，由来自控制光束6.8千兆赫，这个频率被的超精细基态分裂87 Rb的。以制备该频率时，通过激光通过由一个6.8千兆赫的微波源驱动的光纤耦合电光调制器。这会产生边带在6.8 GHz的谐波阵列，上面和下面的载波频率。 </li><li>取得一个探测光束与纯频率，从所有其他不需要的调制边带分离6。8 GHz的光。要做到这一点，使用环形腔之一。锁定腔1的共振+6。8 GHz的边带。这个频率会再通过谐振器被发送，而所有其他的频率被反射，从而制备纯的频率，将解决的铷原子F = 1的基态。腔体可使用本镑-德雷弗霍尔技术27被锁定]时 ，使用从输入反射镜反射的光。 </li><li>分接的激光束在BS3的一部分，并通过AOM2送以允许精细控制的频率和探测光束的强度。那里可用于驱动AOM的几个方法。例如，使用一个可编程的信号发生器设置为产生调制频率为80 MHz高斯脉冲。可替换地，一个脉冲合并连续80 MHz信号在一个RF混频器，得到调制为80兆赫的脉冲。无论哪种方式，该调制高斯然后被放大，并传送到AOM，得到光脉冲到AOM的衍射阶。 注意：此衍射的顺序将提供光的精细控制的脉冲可以存储在存储器中。脉冲的振幅可以通过改变和BS1的分束比对AOM驱动电源的组合进行调整。这允许可靠的生产范围广泛的脉冲振幅，并且特别地，允许生产具有平均光子数小于1 23很微弱的脉冲。 </li><li>下一阶段是重组的探头和控制光束。这可以用一个简单的分束器来完成，但是这将意味着失去了光的某些部分。如果探针和控制的偏振是正交然后无损重组可以使用偏振分束器来实现，但存储才能真正经由探头和控制偏振的独立控制优化。 <ol><li>要做到这一点，使用第二个，高效率，阻抗相匹配，环形腔。设置的空腔，以便探测光束被传输通过，而控制字段是反射离开输出镜。通过这个第二谐振器的传输探头还提供了一个第二层的频率滤波，这有助于避免与四波混频。 </li><li>锁定此腔以使用辅助锁定光束（虚线）被注入模腔的反向模式中的探测光束的频率。调整该光束到一个不同的频率，极化和空间模式的探测光束，以便它可以在检测到反射，而不探测光束产生不利影响。这样做的原因功夫是它是极度困难使用低功率，脉冲探测光束锁定在空腔。控制和探测光束的存储单元之前，准直至7mm和3mm的尺寸，分别为。 </li><li>存储单元之前，控制现场电源为〜270毫瓦和探头电源可以从零选择几个毫瓦根据实验运行。用四分之一波片，调整组合探头和控制光束的偏振是（大约）圆形同一螺旋度和。它们注入到内存气室设备。 </li></ol></li><li>控制用LabVIEW程序28的实验中的所有元素的定时。一个典型的占空比为120微秒。在存储器存储时间关闭加热器，以避免对存储器操作的干扰。一个典型的定时序列示于图4。当可能时，切换控制光束关闭，而光被存储在存储器中。在一个温暖的气室，虽然日ë拉曼过渡从超出多普勒宽度的激发态失谐时，控制字段仍然可以退相干中的存储器的显著源由于自发拉曼散射的概率不为零。拉曼散射是成正比的控制字段的电源和负向失谐的平方。如果控制字段中的整个存储时间保持时，它可以用两个较低状态相互作用并破坏相干性与由散射所定义的指数率。这是在讨论部分进一步解释。 </li><li>存储和调用后，通过探针通过一个过滤单元，以从光束剥去控制字段。它有可能使用使细胞与Rb中的一种天然混合物。 85 Rb的主导和吸收强烈的控制光束频率，提供抑制为60 dB。探测光束的衰减要少得多，通常1.4分贝。使用细胞长75毫米，加热至140℃。用同位素增强85 Rb的A细胞会导致更少的探针吸收。 </li><li>最后一步是在探测脉冲的检测，用的是零差或外差检波。该检测方法的优点在于，它是模式选择这样一些残留控制的光不会对测量结果的影响。回声有一个（接近）圆偏振的是使用half-wave/quarter-wave板组合制成线性的。 <ol><li>以产生本机振荡器，点选断束的一部分在BS4和使用AOM4改变其频率。使用快速示波器的信号从零差和外差设置存储，触发了LabVIEW控制程序。 </li></ol></li></ol>

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Let. 98, 123601 (2007).</li><li>Erhard, M., Helm, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Buffer-gas+effects+on+dark+resonances:+Theory+and+experiment.">Buffer-gas effects on dark resonances: Theory and experiment.</a> Phys. Rev. A. 63, 043813 (2001).</li><li>Balabas, M. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+quality+anti-relaxation+coating+material+for+alkali+atom+vapor+cells.">High quality anti-relaxation coating material for alkali atom vapor cells.</a> Opt. Expr. 18, 5825-5830 (2010).</li><li>Balabas, M. V., Karaulanov, T., Ledbetter, M. P., Budker, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polarized+alkali-metal+vapor+with+minutelong+transverse+spin-relaxation+time.">Polarized alkali-metal vapor with minutelong transverse spin-relaxation time.</a> Phys. Rev. Let. 105, 070801 (2010).</li><li>Buchler, B. C., Hosseini, M., H&#233;tet, G., Sparkes, B. M., Lam, P. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precision+spectral+manipulation+of+optical+pulses+using+a+coherent+photon+echo+memory.">Precision spectral manipulation of optical pulses using a coherent photon echo memory.</a> Opt. Let. 35, 1091-1093 (2010).</li><li>Higginbottom, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Spatial Multimode Storage in a Gradient Echo Memory [dissertation]. , (2012).</li><li>Sparkes, B. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gradient+echo+memory+in+an+ultra-high+optical+depth+cold+atomic+ensemble.">Gradient echo memory in an ultra-high optical depth cold atomic ensemble.</a> arXiv. , (2012).</li></ol>

作者宣称，他们有没有竞争的财务权益。

的必要条件高内存效率是高外径[30]。 Λ-GEM的OD是成正比的拉曼因子Ω_c2 /Δ2，其中Ω_c是耦合场拉比频率和Δ是从激发态拉曼失谐。自发拉曼散射率也成比例的拉曼系数和有故存在折衷实现高吸收和低散射损失之间。为了找到我们使用一个迭代过程控制现场电源，失谐量和气体温度的最佳设置。散射损耗可以在某种程度上减轻由储存期间切断控制光束，经过脉冲被完全吸收。光学厚度也受的原子的内部状态。理想地，我们希望有尽可能多的原子尽可能在F = 1的超精细水平增加探针的吸收。控制光束也发挥了作用在这里，因为它的作用是从F = 2泵原子F = 1的水平。这不是很有效，由于失谐，但控制光束是强大的，可以留在的时间脉冲存储实验之间长时间。拉曼线在我们的实验中，宽度大约是100千赫，这主要是引起控制领域扩大权力的结果。这几乎对应于该原子从F = 2泵送至F = 1超精细状态的速率。但是会有一些人口在MF = 2向左（或-2视圆极化的符号）的超精细级别F = 2，由于缺乏可光学跃迁。 OD值也将强烈的细胞，它决定原子在气相中的数量的温度依赖。我们使用温度约78℃，在小区的中心测量。我们注意到，在我们的细胞，增加超过85°C的温度会导致控制领域的一些吸收以及日的有些语无伦次吸收Ë探头信号。在实验运行过程中的加热器被关闭以避免干扰细胞内的磁场。 两个探头和控制领域的极化在记忆的吸收效率也起到了至关重要的作用。的87Rb的D1的过渡线有两个超精细激发态，共8塞曼能级。原则上，相同的圆偏振光两个探头和控制字段的选择，确保它们仅与激发态能级的mf = 2（或-2），F&#39;= 2交互。激光场的线性或椭圆偏振给通过其他塞曼能级的F&#39;= 1，2上升到拉曼耦合。这将导致在展宽和不对称的拉曼线的形状，由于不同的耦合常数和各种跃迁的交流Stark移位。不幸的是，内存之前准备相同的圆极化探头和控制领域可以体验不同的极化自-R因为他们通过记忆传播otations。这种效应更为明显高OD媒体，我们已经在我们的实验中。这意味着它们的微调探针和控制光束偏振的需要，以抵消自转的影响。 为了进一步使问题复杂化，简并四波混频（FWM）过程中有时可以用大外径25工作时见过。这可能会导致扩增，从而引入噪声到所述存储器的输出状态。尤其是，当线性偏振光同时用于控制和探测光束的FWM效应可以大大由于通过多个激发态的激发拉曼增强。根据该FWM过程要么增强或抑制在我们的系统中的条件列于参考文献25。 FWM产生的影响可以减轻由，再次，微调探头和控制光束的偏振。以这种方式，四波混频过程中可以减少到，他们做的点不增加噪声的回忆光23。相对于FWM，但值得注意的是，这两个腔起到抑制由光纤EOM产生的-6.8吉赫的边带，否则将种子FWM过程中起重要作用。 既自转和FWM影响扩大拉曼线的形状。经过微调，可以实现相当对称的，大致矩形形状的吸收特征， 如图5。与此相反，在图7中被选为极化证明FWM的影响所示的情况。在这里，拉曼特征是高度不对称的。 如前所述，天然丰度的Rb细胞被用于过滤控制光束和探测光束传递至检测部。由于这种电池的高温，我们注意到，周围的单元格窗气流引起变化的外差探测的条纹可见度，重sulting中的信号波动。这种效应被最小化通过实现外差探测滤波细胞后立即和减少围绕单元窗的空气流通过适当的烘箱设计。我们通过过滤细胞观察到的大约30％的探针的损失，由于从窗户菲涅耳反射和吸收通过在过滤单元87 Rb的原子。这个损失可以潜在地通过使用在单元窗的防反射涂层，并使用纯85 Rb的，而不是Rb中的一种天然混合物被减小。 在一个温暖的蒸汽室，扩散到存储时间的主要限制因素之一。吸收光后，原子可扩散的相干区域出来，从而部分地擦除所存储的信息。加入缓冲气体（0.5乇氪，在我们的实验中）降低扩散到一定程度的效果。太多的缓冲气体，但是，会增加碰撞增宽31。这增加了减速oherence和控制字段的吸收，从而降低了上述的泵送效率。另一种方式，以减少横向扩散的效果是通过增大探头和控制字段的横向轮廓，以增加相互作用空间。这种方法最终会通过非弹性碰撞孔壁的限制。在这种情况下，孔壁可以涂有antirelaxation材料32，33，以提供弹性碰撞的墙壁上，因此增强了原子相干时间。通过使用适当的壁涂层和增加激光束的大小几乎覆盖了电池的横截面最小化非弹性碰撞壁，人们会期望从对存储时间的横向扩散的影响最小。然后纵向扩散可能会成为在长期储存的时间占主导地位的消相干效应。纵向扩散导致的原子中的存储时间，可显着降低了reph经历不同的磁场强度ASING效率。控制纵向扩散的一种方法是使用一个冷原子合奏，如已冷却的磁光阱（MOT）的原子。然而，这需要实验的复杂性参与控制冷原子云一个全新的层。这是我们目前正在评估在我们的实验室36的系统。

一个面临量子信息技术的突出挑战是构建量子态内存的能力。对于光子量子计算1，或在一个量子密钥分发系统2中使用的量子中继器，这意味着建立能够存储光3的量子态的存储器。一个实现这一目标所采取的做法是使用可以以这样的方式来存储和控制原子系综然后有控制地在一段时间后释放出可见光。许多技术已经被开发，包括电磁感应透明（EIT）4，原子频率梳（AFC）5，6，7，四波混频（FWM）8，拉曼吸收9，法拉第互动10和光子回波技术，11，12 ，13，14，13，15，16，17，18，19。 本文的重点是Λ - 梯度回波存储（Λ-GEM），使用三个其中工程级“Λ”结构化原子媒体。它最初是在实施一个温暖的铷蒸汽室，2008年20。该方案已被用作随机存取存储器的光脉冲，21，具有明显的效率高达87％22，提供了量子态23的无声的存储和显示了一些承诺作为非线性光学操作24的平台。我们最近还发表了一篇论文，去到一些细节关于这个记忆与温暖的原子蒸气25的相互作用。 该技术的实质是，我们准备原子被非均匀展宽，使得原子会吸收光脉冲的系综。在我们的实验中，我们使用拉曼吸收， 如图1a中 。探测光，这是要被存储，将被映射到原子的2基态之间的相干性。所述扩展是通过施加磁场gradien提供吨沿光传播的方向，诱导的拉曼吸收峰的频率的空间梯度， 如图1b所示 。因此，所存储的脉冲的不同频率分量被映射到不同空间位置线性地沿着原子合奏的长度。换句话说，这是通过对输入脉冲的吸收所产生的原子自旋波的空间分布是成正比的傅立叶输入脉冲的时间轮廓的变换。我们将在后面勾勒，它是这个频率梯度也使一些本内存的有趣光谱处理能力。通过反转磁场梯度，该原子系综的相干性的演化可以是时间反演。这使得光的脉冲的检索。

<table border="0" cellpadding="0" cellspacing="0" width="596">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Titanium-sapphire laser</td>
			<td style="width:95px;">M Squared Lasers</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">SolsTiS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Digital oscilloscope</td>
			<td style="width:95px;">Lecroy</td>
			<td style="width:119px;"></td>
			<td>WaveRunner 44Xi-A</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Memory cell</td>
			<td style="width:95px;">Triad Technology</td>
			<td style="width:119px;"></td>
			<td>20 cm long, 87Rb enhanced, 0.5 Torr Kr buffer gas, AR-coated</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Filter cell</td>
			<td style="width:95px;">Triad Technology</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">7.5 cm long, natural mixture Rb, no buffer gas</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Fiber EOM</td>
			<td style="width:95px;">EOSPACE</td>
			<td style="width:119px;"></td>
			<td>PM-0K5-10-PFA-UL</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">AOM</td>
			<td style="width:95px;">AA Opto-Electronic</td>
			<td style="width:119px;"></td>
			<td>MT80-A1-IR</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">AOM drive components</td>
			<td style="width:95px;">Minicircuits</td>
			<td style="width:119px;"></td>
			<td>Amplifier ZHL-1-2W</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:95px;">Minicircuits</td>
			<td style="width:119px;"></td>
			<td>Mixer ZAD-6</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:95px;">Agilent</td>
			<td style="width:119px;"></td>
			<td>80 MHz signal source 33250A</td>
		</tr>
		<tr height="189">
			<td height="189" style="height:189px;width:216px;">Cavities</td>
			<td style="width:95px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Custom made triangular ring cavity. FSR = 600 MHz, Finesse = 100. 
			Flat mirrors (for input and output) IBS coating by Advanced Thin Films. Back mirror is 1 m ROC 
			Newport Supermirror (R&#62;99.97%)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Photodiodes</td>
			<td style="width:95px;">Hamamatsu</td>
			<td style="width:119px;"></td>
			<td>S3883</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Current Switches</td>
			<td style="width:95px;">Electronic Design and Research</td>
			<td style="width:119px;"></td>
			<td>EDR83915/2 and EDR8276612</td>
		</tr>
	</tbody>
</table>

gradient echo quantum memory in warm atomic vapor

梯度回波存储（创业板）是一种协议，用于存储光的光量子态的原子系综。的主要动机这样的技术是量子密钥分配（QKD），它使用海森堡不确定性，以保证密码密钥的安全性，在传输距离受到限制。一个量子中继器的发展是一个可能的路径延伸的QKD范围，但是一个中继器将需要一个量子存储器。在我们的实验中，我们使用的铷87蒸气中所包含的温暖气体单元的气体。这使得该计划特别简单。它也是一个高度灵活的方案，使内存细化所存储的状态的，例如频移和带宽操作。创业板协议的基础是吸收光成乃磁场梯度原子的合奏。这个梯度的逆转导致原子极化的重新安排，因此召回存储的光学状态。 WË将概述我们如何准备的原子，这种梯度，也介绍了一些需要避免的，尤其是四波混频，它可以产生光学增益的陷阱。

1。用拉曼吸收作为诊断工具第一个结果获得的是探​​测光束的拉曼线的吸收。这种吸收功能优化去实现最佳内存性能很长的路要走。与磁梯度线圈断开时，控制频率可以扫描在弱连续探测波的存在。探测光束的吸收是直接相关的原子单元的光密度。基于这一点，该单元格，功率控制束和单光子失谐的温度可以通过一个迭代过程进行优化，以得到最佳的拉曼吸收。过多的控制束功率会增加吸收，也拓宽了线的宽度。当优化，宽度为100千赫在我们的系统中的顺序。 开关上的梯度线圈一会拓宽拉曼线。加宽吸收的宽度阻止地雷的存储器的带宽。一个折衷然后必须被光密度，从而影响记忆效率和内存带宽之间进行。所述探针传输示为我们在图5中，其中所述存储器带宽被设定为约1 MHz的扩大拉曼线之一。 在同一时间开关在两个磁场梯度线圈，该nonbroadened吸收线宽应回收。任何不匹配的电流大小或磁场的空间非均匀性会直接反映的拉曼吸收范围扩大和变形。 2。脉冲存储对所述存储器中的最简单的配置是单个脉冲的存储和检索。这将是，例如，存储时间为2微秒的脉冲和开关的磁场梯度线圈3微秒的脉冲峰值后， 如图6。如果光密度低，一些光leakaGE将取决于介质的光学密度（OD）进行观察。仔细调整内存参数是必不可少的获得高效率的存储。这包括的存储单元温度的优化，探头和控制字段之间的仔细对准，调谐控制光束的强度，以找到吸收和散射之间的最佳折衷，确保了光束的正确偏振和调谐的频率探头和控制光束。这种优化方法是在讨论部分进一步解释。效率超过80％，为4微秒22存储时间可以当所有这些参数都调整好预期。存储的效率被定义为回顾回波的能量，并且还没有被存储在存储器中的相同脉冲的能量之间的比例。这有效地抽取出的线性损失的影响，例如由于表面或absorpt上的菲涅耳反射离子在过滤单元。当使用外差探测，所述脉冲的能量通过平方差信号和测量脉冲的包络的面积测量。 所检索的脉冲的频率和带宽取决于注入梯度线圈的电流。简单操作这些电流的允许检索脉冲的微调。更复杂的频谱操作（如在29所概述）可以使用更先进的线圈的设置，其中沿所述存储器中的梯度可以被独立地调节与位置和时间的函数来完成。 <img alt="图1" fo:content-width="6in" src="/files/ftp_upload/50552/50552fig1.jpg" width="500px" /> 图1。 a）在在内存中使用的铷87日1线水平方案 。探测光的拉曼吸收来创建相干赌注<html>吐温在F = 1和F = 2接地状态。 二）磁场梯度给出了基态的空间依赖失谐沿该单元的长度。反转梯度和转动控制横梁上给出了存储的探测光的回忆。 （摘自[34]）。 <a href="https://www.jove.com/files/ftp_upload/50552/50552fig1highres.jpg" target="_blank">点击这里查看大图</a> 。 <img alt="图2" fo:content-width="6in" src="/files/ftp_upload/50552/50552fig2.jpg" width="500px" /> 图2原理的光学模清洁剂。请参考说明的方法部分。 <a href="https://www.jove.com/files/ftp_upload/50552/50552fig2highres.jpg" target="_blank">点击这里查看大图</a> 。 ig3.jpg“宽度=”500px的“/&gt; 图3。原理实验装置的 AOM =声光调制器; EOM =电光调制器; BS =分束器，λ/ 4 =四分之一波片。 <a href="https://www.jove.com/files/ftp_upload/50552/50552fig3highres.jpg" target="_blank">点击这里查看大图</a> 。 <img alt="图4" fo:content-width="6in" src="/files/ftp_upload/50552/50552fig4.jpg" width="500px" /> 图4。在存储器中的典型时序。（从35拍摄）。 <a href="https://www.jove.com/files/ftp_upload/50552/50552fig4highres.jpg" target="_blank">点击这里查看大图</a> 。 <img alt="图5" fo:content-width="6in" src="/files/ftp_upload/50552/50552fig5.jpg" width="500px" /> 图5。典型的外差扩大拉曼线时，日之一利安达磁电梯度线圈接通，数据（细实线）采用外差测量。振荡是由于在探测光和本地振荡光之间的节拍。虚线曲线示出了该数据是加宽的拉曼线的形状的包络线。 （25修正）。 <a href="https://www.jove.com/files/ftp_upload/50552/50552fig5highres.jpg" target="_blank">点击这里查看大图</a> 。 <img alt="图6" fo:content-width="6in" src="/files/ftp_upload/50552/50552fig6.jpg" width="500px" /> 图6。典型的平均效率GEM回波短存储时间的磁场梯度线圈被接通了在t = 10微秒（虚线）。红色：输入脉冲强度分布。蓝色：记忆的强度输出，展现漏光（其中红色输入脉冲下明显），并回顾回声，这似乎T的权利他虚线。 <a href="https://www.jove.com/files/ftp_upload/50552/50552fig6highres.jpg" target="_blank">点击这里查看大图</a> 。 <img alt="图7" fo:content-width="6in" src="/files/ftp_upload/50552/50552fig7.jpg" width="500px" /> 图7。四波混频效应，扫描拉曼线，用于各种控制领域的权力和电池的温度时，对于这个数字只是，控场和探测光束的偏振进行选择，使他们最大限度地发挥作用。 PC是控制光束功率。 （25修正）。 <a href="https://www.jove.com/files/ftp_upload/50552/50552fig7highres.jpg" target="_blank">点击这里查看大图</a> 。

Watch this Scientific Journal Video about Gradient Echo Quantum Memory in Warm Atomic Vapor at JoVE.com

Gradient Echo Quantum Memory in Warm Atomic Vapor

梯度回波存储是一个协议，用于存储光的光量子态的原子系综。量子存储器是量子中继器的关键元件，它可以扩展量子密钥分配的范围。我们勾勒出计划的运作在一个3级的原子系综实现时。

梯度回波量子存储在温暖的原子蒸气

Gradient  echo memory (GEM) is a protocol for storing optical quantum states of light in  atomic ensembles. The primary motivation for such a technology ...

gradient-echo-quantum-memory-in-warm-atomic-vapor

Research

JoVE Journal

Engineering

12.7K 次观看.  The Australian National University. 梯度回波存储是一个协议，用于存储光的光量子态的原子系综。量子存储器是量子中继器的关键元件，它可以扩展量子密钥分配的范围。我们勾勒出计划的运作在一个3级的原子系综实现时。 

视频: Gradient Echo Quantum Memory in Warm Atomic Vapor

Compact Quantum Dots for Single-molecule Imaging

Single-molecule imaging is an important tool for understanding the mechanisms of biomolecular function and for visualizing the spatial and temporal heterogeneity of molecular behaviors that underlie cellular biology 1-4. To image an individual molecule of interest, it is typically conjugated to a fluorescent tag (dye, protein, bead, or quantum dot) and observed with epifluorescence or total internal reflection fluorescence (TIRF) microscopy. While dyes and fluorescent proteins have been the mainstay of fluorescence imaging for decades, their fluorescence is unstable under high photon fluxes necessary to observe individual molecules, yielding only a few seconds of observation before complete loss of signal. Latex beads and dye-labeled beads provide improved signal stability but at the expense of drastically larger hydrodynamic size, which can deleteriously alter the diffusion and behavior of the molecule under study.
Quantum dots (QDs) offer a balance between these two problematic regimes. These nanoparticles are composed of semiconductor materials and can be engineered with a hydrodynamically compact size with exceptional resistance to photodegradation 5. Thus in recent years QDs have been instrumental in enabling long-term observation of complex macromolecular behavior on the single molecule level. However these particles have still been found to exhibit impaired diffusion in crowded molecular environments such as the cellular cytoplasm and the neuronal synaptic cleft, where their sizes are still too large 4,6,7.
Recently we have engineered the cores and surface coatings of QDs for minimized hydrodynamic size, while balancing offsets to colloidal stability, photostability, brightness, and nonspecific binding that have hindered the utility of compact QDs in the past 8,9. The goal of this article is to demonstrate the synthesis, modification, and characterization of these optimized nanocrystals, composed of an alloyed HgxCd1-xSe core coated with an insulating CdyZn1-yS shell, further coated with a multidentate polymer ligand modified with short polyethylene glycol (PEG) chains (Figure 1). Compared with conventional CdSe nanocrystals, HgxCd1-xSe alloys offer greater quantum yields of fluorescence, fluorescence at red and near-infrared wavelengths for enhanced signal-to-noise in cells, and excitation at non-cytotoxic visible wavelengths. Multidentate polymer coatings bind to the nanocrystal surface in a closed and flat conformation to minimize hydrodynamic size, and PEG neutralizes the surface charge to minimize nonspecific binding to cells and biomolecules. The end result is a brightly fluorescent nanocrystal with emission between 550-800 nm and a total hydrodynamic size near 12 nm. This is in the same size range as many soluble globular proteins in cells, and substantially smaller than conventional PEGylated QDs (25-35 nm).

We describe the preparation of colloidal quantum dots with minimized hydrodynamic size for single-molecule fluorescence imaging. Compared to conventional quantum dots, these nanoparticles are similar in size to globular proteins and are optimized for single-molecule brightness, stability against photodegradation, and resistance to nonspecific binding to proteins and cells.

紧凑型量子点的单分子成像

Single-molecule imaging is an important tool for  understanding the mechanisms of biomolecular function and for visualizing the  spatial and temporal ...

科研

工程学

Echo Particle Image Velocimetry

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 Consequently, a prerequisite for understanding, predicting, and controlling fluid flows is the capability to measure the velocity field with adequate spatial and temporal resolution.2 For velocity measurements in optically opaque fluids or through optically opaque geometries, echo particle image velocimetry (EPIV) is an attractive diagnostic technique to generate "instantaneous" two-dimensional fields of velocity.3,4,5,6 In this paper, the operating protocol for an EPIV system built by integrating a commercial medical ultrasound machine7 with a PC running commercial particle image velocimetry (PIV) software8 is described, and validation measurements in Hagen-Poiseuille (i.e., laminar pipe) flow are reported.
For the EPIV measurements, a phased array probe connected to the medical ultrasound machine is used to generate a two-dimensional ultrasound image by pulsing the piezoelectric probe elements at different times. Each probe element transmits an ultrasound pulse into the fluid, and tracer particles in the fluid (either naturally occurring or seeded) reflect ultrasound echoes back to the probe where they are recorded. The amplitude of the reflected ultrasound waves and their time delay relative to transmission are used to create what is known as B-mode (brightness mode) two-dimensional ultrasound images. Specifically, the time delay is used to determine the position of the scatterer in the fluid and the amplitude is used to assign intensity to the scatterer. The time required to obtain a single B-mode image, t, is determined by the time it take to pulse all the elements of the phased array probe. For acquiring multiple B-mode images, the frame rate of the system in frames per second (fps) = 1/&delta;t. (See 9 for a review of ultrasound imaging.)
For a typical EPIV experiment, the frame rate is between 20-60 fps, depending on flow conditions, and 100-1000 B-mode images of the spatial distribution of the tracer particles in the flow are acquired. Once acquired, the B-mode ultrasound images are transmitted via an ethernet connection to the PC running the PIV commercial software. Using the PIV software, tracer particle displacement fields, D(x,y)[pixels], (where x and y denote horizontal and vertical spatial position in the ultrasound image, respectively) are acquired by applying cross correlation algorithms to successive ultrasound B-mode images.10 The velocity fields, u(x,y)[m/s], are determined from the displacements fields, knowing the time step between image pairs, &Delta;T[s], and the image magnification, M[meter/pixel], i.e., u(x,y) = MD(x,y)/&Delta;T. The time step between images &Delta;T = 1/fps + D(x,y)/B, where B[pixels/s] is the time it takes for the ultrasound probe to sweep across the image width. In the present study, M = 77[&mu;m/pixel], fps = 49.5[1/s], and B = 25,047[pixels/s]. Once acquired, the velocity fields can be analyzed to compute flow quantities of interest.

An echo particle image velocimetry (EPIV) system capable of acquiring two-dimensional fields of velocity in optically opaque fluids or through optically opaque geometries is described, and validation measurements in pipe flow are reported.

回声粒子图像测速技术

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 ...

Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and entanglement, to solve certain problems exponentially faster than with the best known algorithms on a classical computer. Gate-defined lateral quantum dots on GaAs/AlGaAs are one of many avenues explored for the implementation of a qubit. When properly fabricated, such a device is able to trap a small number of electrons in a certain region of space. The spin states of these electrons can then be used to implement the logical 0 and 1 of the quantum bit. Given the nanometer scale of these quantum dots, cleanroom facilities offering specialized equipment- such as scanning electron microscopes and e-beam evaporators- are required for their fabrication. Great care must be taken throughout the fabrication process to maintain cleanliness of the sample surface and to avoid damaging the fragile gates of the structure. This paper presents the detailed fabrication protocol of gate-defined lateral quantum dots from the wafer to a working device. Characterization methods and representative results are also briefly discussed. Although this paper concentrates on double quantum dots, the fabrication process remains the same for single or triple dots or even arrays of quantum dots. Moreover, the protocol can be adapted to fabricate lateral quantum dots on other substrates, such as Si/SiGe.

This paper presents a detailed fabrication protocol for gate-defined semiconductor lateral quantum dots on gallium arsenide heterostructures. These nanoscale devices are used to trap few electrons for use as quantum bits in quantum information processing or for other mesoscopic experiments such as coherent conductance measurements.

纳米加工门定义的GaAs / AlGaAs多量子点横向

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and ...

Analysis of Contact Interfaces for Single GaN Nanowire Devices

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit a strong degradation after annealing due to the occurrence of void formation at the contact/SiO2 interface. This void formation can cause cracking and delamination of the metal film, which can increase the resistance or lead to a complete failure of the NW device. In order to address issues associated with void formation, a technique was developed that removes Ni/Au contact metal films from the substrates to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN NW devices. This procedure determines the degree of adhesion of the contact films to the substrate and NWs and allows for the characterization of the morphology and composition of the contact interface with the substrate and nanowires. This technique is also useful for assessing the amount of residual contamination that remains from the NW suspension and from photolithographic processes on the NW-SiO2 surface prior to metal deposition. The detailed steps of this procedure are presented for the removal of annealed Ni/Au contacts to Mg-doped GaN NWs on a SiO2 substrate.

A technique was developed that removes Ni/Au contact metal films from their substrate to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN nanowire devices.

单氮化镓纳米线设备分析接触界面

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit  a strong degradation after annealing due to the  occurrence of void formation at the ...

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

使用中子自旋回声解决放牧发生率散射调查有机太阳能电池材料

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

Construction and Characterization of External Cavity Diode Lasers for Atomic Physics

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs1,2. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling1,2 makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman3, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included.

This is an instructional paper to guide the construction and diagnostics of external cavity diode lasers (ECDLs), including component selection and optical alignment, as well as the basics of frequency reference spectroscopy and laser linewidth measurements for applications in the field of atomic physics.

外腔半导体激光器的原子物理的构建与鉴定

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and ...

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states are indeed the resources for implementing various protocols, ranging from enhanced metrology to quantum communication and computing. A variety of devices can be used to generate non-classical states, such as single emitters, light-matter interfaces or non-linear systems3. We focus here on the use of a continuous-wave optical parametric oscillator3,4. This system is based on a non-linear &#967;2 crystal inserted inside an optical cavity and it is now well-known as a very efficient source of non-classical light, such as single-mode or two-mode squeezed vacuum depending on the crystal phase matching. 
Squeezed vacuum is a Gaussian state as its quadrature distributions follow a Gaussian statistics. However, it has been shown that number of protocols require non-Gaussian states5. Generating directly such states is a difficult task and would require strong &#967;3 non-linearities. Another procedure, probabilistic but heralded, consists in using a measurement-induced non-linearity via a conditional preparation technique operated on Gaussian states. Here, we detail this generation protocol for two non-Gaussian states, the single-photon state and a superposition of coherent states, using two differently phase-matched parametric oscillators as primary resources. This technique enables achievement of a high fidelity with the targeted state and generation of the state in a well-controlled spatiotemporal mode.

We describe the reliable generation of non-Gaussian states of traveling optical fields, including single-photon states and coherent state superpositions, using a conditional preparation method operated on the non-classical light emitted by optical parametric oscillators. Type-I and type-II phase-matched oscillators are considered and common procedures, such as the required frequency filtering or the high-efficiency quantum state characterization by homodyning, are detailed.

光与连续波光学参量振荡器的量子态工程

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

硅表面润湿性的选择区域改性脉冲紫外激光照射在液体环境

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization.

The fabrication process and experimental characterization techniques relevant to single-electron pumps based on silicon metal-oxide-semiconductor quantum dots are discussed.

硅金属 - 氧化物 - 半导体量子点单电子泵

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by ...

Experimental Procedure for Warm Spinning of Cast Aluminum Components

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to improve material properties. With a wide array of processing parameters which can affect both the shape attained and resulting material properties, this type of processing is notoriously difficult to commission. A simplified, light-duty version of the process has been designed and implemented for full-size automotive wheels. The apparatus is intended to assist in understanding the deformation mechanisms and the material response to this type of processing. An experimental protocol has been developed to prepare for, and subsequently perform forming trials and is described for as-cast A356 wheel blanks. The thermal profile attained, along with instrumentation details are provided. Similitude with full-scale forming operations which impart significantly more deformation at faster rates is discussed.

An experimental protocol for instrumented warm rotary forming of cast aluminum alloys employing a bespoke industrially scaled apparatus is presented. Experimental considerations including thermal and mechanical effects are discussed, as well as similitude with full-scale processing of automotive wheels.

铸铝零部件的暖纺纱实验程序

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to ...