Quantum technologies for inertial sensing

我们的社会在很大程度上依赖全球定位系统（GPS）来促进支持我们经济的供应线，使货物和人员在不熟悉的地方流动，帮助维护电力网络，并支持我们的应急服务和军队。GPS的工作原理是，在我们头顶上方2万公里处环绕地球运行的卫星网络将信号发送到地球上的接收器，接收器可以以几米的精度确定位置。然而，GPS不提供一个故障安全系统来确定位置。它不能在地下或水下工作，因为它依赖于从太空发送到我们的手机、汽车或其他卫星导航设备上的接收器的信号，所以它很容易受到当地天气条件的影响，容易被欺骗和被阻挡。为了克服GPS的弱点，我将开发一种新型的定位服务，它利用量子物理来确定位置，而不需要向其他人发送或接收信号。我不使用环绕地球的卫星网络来导航，而是使用原子云中的电子轨道。原子是很好的传感器，因为特定元素的每个原子都是相同的。这意味着无论它们的局部环境如何，原子传感器都以相同的方式工作。它们是预先校准的，所以不同的传感器总是相互一致的，而且与电子设备不同，它们不会随着时间的推移而老化或磨损。然而，为了描述原子传感器的行为，我们需要使用量子力学。根据量子力学，像电子、原子甚至分子这样的粒子表现得像波一样，可以探索空间的扩展区域，甚至可以同时出现在两个地方——这被称为量子叠加。量子叠加非常脆弱，这就是为什么我们在日常生活中看不到它们的原因。然而，通过将原子冷却到极低的温度，并将它们储存在一个保护装置中，我们可以创造一个环境，让它们得以保存，甚至为我们所用。我的新定位装置通过使用精心控制的激光脉冲将原子云置于叠加状态来工作。如果容纳原子云的保护室在移动，那么叠加态就会受到轻微的干扰，原子中的电子轨道就会改变。当这种情况发生时，原子可以吸收的光的数量也会发生变化，而变化的数量仅取决于保护腔的移动速度。如果我们非常精确地测量原子在一段时间内吸收了多少光，我们就可以计算出载着它们的交通工具如何移动，从而计算出它移动了多远。只要你知道你在哪里当你第一次开始测量的时候，你就会知道你在哪里，而不需要给别人发信号。

Our society relies heavily on the Global Positioning System (GPS) to facilitate the supply lines that support our economy, to enable the movement of goods and people in unfamiliar places, to help maintain power networks, and support our emergency services and military. GPS works by sending signals from a network of satellites orbiting the earth 20,000km above our heads to receivers on Earth, which can determine position with an accuracy of a few metres. However, GPS does not provide a fail-safe system for determining position. It doesn't work under ground or under water and because it relies on signals being sent from space to receivers in our phones, cars or other sat-nav enabled devices, it's vulnerable to local weather conditions, spoofing and being blocked. To overcome the vulnerabilities of GPS I'm going to develop a new type of location service that harnesses quantum physics to determine position without the need to send or receive signals to someone else. Instead of using a network of satellites orbiting the earth in order to navigate, I am going to use electron orbitals in clouds of atoms. Atoms make very good sensors because each atom of a particular element is identical. This means that atomic sensors all behave in the same way no matter what their local environment. They come pre-calibrated, so different sensors will always agree with one another, and unlike electronic devices they do not age or wear out over time. However, in order to describe the behavior of atomic sensors we need to use quantum mechanics.According to quantum mechanics particles such as electrons, atoms and even molecules behave like waves that can explore extended areas of space and can even be in two places at once - called a quantum superposition. Quantum superpositions are extremely fragile, which is why we don't observe them in our everyday lives. However, by cooling atoms down to extremely low temperatures and storing them inside a protective apparatus we can create an environment where they be can preserved, and even used to our advantage. My new location device works by placing a cloud of atoms in a superposition using carefully controlled pulses of laser light. If the protective chamber housing the cloud of atoms is moving then the superposition will be disturbed very slightly, and the electron orbitals in the atoms will change. When this happens the amount of light that the atoms can absorb will also change, and by an amount that depends only on how fast the protective chamber is moving. If we measure very precisely how much light the atoms absorb over time, we can calculate how the vehicle carrying them is moving and how therefore how far it has moved. As long as you know where you were you were when you first started measuring, you'll always then know where you are and all without ever having to send a signal to anyone else.