正文翻譯

Quantum computing may have shown its “supremacy” over classical computing a little over a year ago, but it still has a long way to go. Intel’s director of quantum hardware, Jim Clarke, says that quantum computing will really have arrived when it can do something unique that can change our lives, calling that point “quantum practicality.” Clarke talked to IEEE Spectrum about how he intends to get silicon-based quantum computers there:
Jim Clarke on…
Why quantum computers will be made of silicon
How silicon spin qubits work
What needs to happen before quantum error correction works
“Hot” silicon spin qubits
What problems keep him up at night

量子計(jì)算可能在一年多前就已經(jīng)顯示出它對經(jīng)典計(jì)算的“霸權(quán)”，但它還有很長的路要走。 英特爾的量子硬件主管吉姆·克拉克(Jim Clarke)說，當(dāng)量子計(jì)算能夠做出一些獨(dú)特的改變我們生活的事情時，它才會真正地到來，我們稱這一點(diǎn)為“量子實(shí)用性”。克拉克對IEEE Spectrum闡述了他打算如何建造基于硅的量子計(jì)算機(jī)，包括：
為什么量子計(jì)算機(jī)將由硅制成
硅自旋量子比特是如何工作的
實(shí)現(xiàn)量子糾錯前需要發(fā)生的事情
“熱”硅自旋量子比特
什么問題讓他晚上睡不著覺

IEEE Spectrum: Intel seems to have shifted focus from quantum computers that rely on superconducting qubits to ones with silicon spin qubits. Why do you think silicon has the best chance of leading to a useful quantum computer?

IEEE Spectrum: 英特爾似乎已經(jīng)將焦點(diǎn)從依賴超導(dǎo)量子比特的量子計(jì)算機(jī)轉(zhuǎn)移到使用硅自旋量子比特的量子計(jì)算機(jī)上。 你為什么認(rèn)為硅最有可能導(dǎo)致一臺有用的量子計(jì)算機(jī)？

We’re currently making server chips with billions and billions of transistors on them. So if our spin qubit is about the size of a transistor, from a form-factor and energy perspective, we would expect it to scale much better.

我們目前正在生產(chǎn)服務(wù)器芯片，上面有數(shù)十億個晶體管。 因此，如果我們的自旋量子比特是一個晶體管的大小，從構(gòu)造倍數(shù)和能量的角度來看，我們預(yù)計(jì)它能夠更好地規(guī)模化。

Spectrum: What are silicon spin qubits and how do they differ from competing technology, such as superconducting qubits and ion trap systems?

Spectrum: 什么是硅自旋量子比特，它們與超導(dǎo)量子比特和離子阱系統(tǒng)等競爭技術(shù)有何不同？

We do something similar with the spin qubit, but it’s a little different. You turn on a transistor, and you have a flow of electrons from one side to another. In a silicon spin qubit, you essentially trap a single electron in your transistor, and then you put the whole thing in a magnetic field [using a superconducting electromagnet in a refrigerator]. This orients the electron to either spin up or spin down. We are essentially using its spin state as the zero and one of the qubit.

我們做了一些類似自旋量子比特的東西，但也有點(diǎn)不同。 你打開一個晶體管，你有電子從一邊流向另一邊。 在硅自旋量子比特中，你基本上是在晶體管中捕獲了一個電子，然后把整個東西放在磁場中[在制冷機(jī)中使用超導(dǎo)電磁鐵]。 這使電子要么自旋向上，要么自旋向下。 我們基本上使用它的自旋狀態(tài)作為量子比特的0態(tài)和1態(tài)。

That would be an individual qubit. Then with very good control, we can get two separated electrons in close proximity and control the amount of interaction between them. And that serves as our two-qubit interaction.

這將是一個單獨(dú)的量子比特。 然后，在很好的控制下，我們可以將兩個分離的電子靠近，并控制它們之間相互作用的大小。 這就是我們的兩量子比特之間的相互作用。

So we’re basically taking a transistor, operating at the single electron level, getting it in very close proximity to what would amount to another transistor, and then we’re controlling the electrons.

因此，我們基本上是將單個電子水平上工作的一個晶體管，使它非常接近另一個晶體管，然后我們控制電子間的相互作用。

Spectrum: Does the proximity between adjacent qubits limit how the system can scale?

Spectrum: 相鄰量子比特之間的接近是否限制了系統(tǒng)如何規(guī)?；?/p>

Clarke: I’m going to answer that in two ways. First, the interaction distance between two electrons to provide a two-qubit gate is not asking too much of our process. We make smaller devices every day at Intel. There are other problems, but that’s not one of them.

Clarke: 我要用兩種方式來回答這個問題。 首先，控制兩個電子之間的相互作用距離來實(shí)現(xiàn)兩量子比特門操作，并不要求我們太多的處理。 我們在英特爾每天都生產(chǎn)更小的設(shè)備。 這里有其他的問題，但這不是其中之一。

Typically, these qubits operate on a sort of a nearest-neighbor interaction. So you might have a two-dimensional grid of qubits, and you would essentially only have interactions between one of its nearest neighbors. And then you would build up [from there]. That qubit would then have interactions with its nearest neighbors and so forth. And then once you develop an entangled system, that’s how you would get a fully entangled 2D grid. [Entanglement is a condition necessary for certain quantum computations.]

通常，這些量子比特是在一種最近鄰相互作用下工作的。 因此，你可能有一個二維網(wǎng)格化的量子比特陣列，你基本上只會讓一對近鄰之間的量子比特有相互作用。 量子比特將與其最近的鄰居相互作用等等。 然后，一旦你制造出了一個處于糾纏的系統(tǒng)，你就得到一個完全糾纏的二維網(wǎng)格[糾纏是某些量子計(jì)算所必需的條件]

Spectrum: What are some of the difficult issues right now with silicon spin qubits?

Spectrum: 目前硅自旋量子比特的一些難題是什么？

Clarke: By highlighting the challenges of this technology, I’m not saying that this is any harder than other technologies. I’m prefacing this, because certainly some of the things that I read in the literature would suggest that qubits are straightforward to fabricate or scale. Regardless of the qubit technology, they’re all difficult.

Clarke: 通過強(qiáng)調(diào)這項(xiàng)技術(shù)的挑戰(zhàn)，我并不是說這比其他技術(shù)更難。 我先說這個是因?yàn)槲以谖墨I(xiàn)中讀到的一些東西說量子比特的制備和規(guī)?；呛唵蚊髁说?。不管何種量子比特技術(shù)，它們都是困難的。

With a spin qubit, we take a transistor that normally has a current of electrons go through, and you operate it at the single electron level. This is the equivalent of having a single electron, placed into a sea of several hundred thousand silicon atoms and still being able to manipulate whether it’s spin up or spin down.

單個自旋量子比特，意味著將通常有電子流通的晶體管在單電子水平上操作它。 這相當(dāng)于放置在一個由幾十萬個硅原子組成的海洋中的單個電子，無論它的自旋是向上還是向下，你仍然能夠操縱它。

So we essentially have a small amount of silicon, we’ll call this the channel of our transistor, and we’re controlling a single electron within that piece of silicon. The challenge is that silicon, even a single crystal, may not be as clean as we need it. Some of the defects—these defects can be extra bonds, they can be charge defects, they can be dislocations in the silicon—these can all impact that single electron that we’re studying. This is really a materials issue that we’re trying to solve.

所以我們本質(zhì)上有少量的硅，我們稱之為晶體管的通道，我們控制的是硅內(nèi)的單個電子。 挑戰(zhàn)是，硅，甚至是單晶硅，可能達(dá)不到我們需要的那種純度。 一些缺陷-這些缺陷可以是額外的鍵，它們可以是電荷缺陷，它們可以是硅中的位錯-這些都可以影響我們正在研究的單個電子。 這確實(shí)是我們試圖解決的一個材料問題。

Spectrum: Just briefly, what is coherence time and what’s its importance to computing?

Spectrum: 簡單地說，什么是相干時間，它對計(jì)算的重要性是什么？

What needs to happen [to compensate for brief coherence times] is that we need to develop an error correction technique. That’s a complex way of saying we’re going to put together a bunch of real qubits and have them function as one very good logical qubit.

為了對抗短暫的相干時間，我們需要開發(fā)糾錯技術(shù)。 這是一種復(fù)雜的方法，我們要把一堆物理的量子比特組合起來，讓它們作為一個非常好的邏輯量子比特來發(fā)揮作用。

Spectrum: How close is that kind of error correction?

Spectrum: 這種糾錯離我們有多近？

Clarke: It was one of the four items that really needs to happen for us to realize a quantum computer that I wrote about earlier. The first is we need better qubits. The second is we need better interconnects. The third is we need better control. And the fourth is we need error correction. We still need improvements on the first three before we’re really going to get, in a fully scalable manner, to error correction.

Clarke: 這是我早些時候?qū)懙降囊獙?shí)現(xiàn)一個量子計(jì)算機(jī)我們真正需要實(shí)現(xiàn)的四個要素之一。 首先，我們需要更好的量子比特。 第二是我們需要更好的互連。 第三是我們需要更好的控制。 第四是我們需要糾錯。 在我們真正能夠完全以擴(kuò)展的方式進(jìn)行糾錯之前，我們?nèi)匀恍枰獙η叭齻€要素進(jìn)行改進(jìn)。

You will see groups starting to do little bits of error correction on just a few qubits. But we need better qubits and we need a more efficient way of wiring them up and controlling them before you’re really going to see fully fault-tolerant quantum computing.

您將看到一些小組開始在幾個量子比特上進(jìn)行小的糾錯。 但我們需要更好的量子比特，我們需要一種更有效的方法來連接它們并控制它們，然后你才能真正看到完全容錯的量子計(jì)算。

Spectrum: One of the improvements to qubits recently was the development of “hot” silicon qubits. Can you explain their significance?

Spectrum: 最近對量子比特的改進(jìn)之一是開發(fā)了“熱”硅量子比特。 你能解釋一下它們的意義嗎？

Now, imagine if we can operate our qubit slightly warmer. And by slightly warmer, I mean maybe 1 kelvin. All of a sudden, the cooling capacity of our fridge becomes much greater. The cooling capacity of our fridge at 10 millikelvin is roughly a milliwatt. That's not a lot of power. At 1 kelvin, it’s probably a couple of watts. So, if we can operate at higher temperatures, we can then place control electronics in very close proximity to our qubit chip.

現(xiàn)在，想象一下，如果我們能夠在稍微溫暖一點(diǎn)的溫度下操作我們的量子比特。 稍微暖和一點(diǎn)，我是說1開爾文。 這意味著我們制冷機(jī)的冷卻容量突然變大了。 我們的制冷機(jī)在10毫開爾文的冷卻能力大約是1毫瓦。 那不是很大的功率。 在1開爾文，冷卻能力可能是幾瓦。 因此，如果我們能在更高的溫度下工作，那么我們就可以把控制電子放置在非常接近我們的量子比特芯片的地方。

Spectrum: Are hot qubits structurally the same as regular silicon spin qubits?

Spectrum: 熱量子比特在結(jié)構(gòu)上是否與通常的硅自旋量子比特相同？

Clarke: Within silicon spin qubits, there are several different types of materials, some are what I would call silicon MOS-type qubits— very similar to today’s transistor materials. In other silicon spin qubits you have silicon that’s buried below a layer of silicon germanium. We’ll call that a buried channel device. Each have their benefits and challenges.

Clarke: 在硅自旋量子比特中，有幾種不同類型的材料，有些是我所說的硅MOS型量子比特-非常類似于今天的晶體管材料。 在其他硅自旋量子比特中，硅被埋在一層硅鍺下面。 我們把它叫做暗埋通道裝置。 每種都有自己的優(yōu)點(diǎn)和挑戰(zhàn)。

We’ve done a lot of work with TU Delft working on a certain type of [silicon MOS] material system, which is a little different than most in the community are studying [and lets us] operate the system at a slightly higher temperature.

我們和代爾夫特工業(yè)大學(xué)已經(jīng)在某種類型的[硅MOS]材料系統(tǒng)做了很多工作，它與大多數(shù)同行正在研究的有點(diǎn)不同，它使我們能夠在一個稍高的溫度操縱系統(tǒng)。

I loved the quantum supremacy work. I really did. It’s good for our community. But it’s a contrived problem, on a brute force system, where the wiring is a mess (or at least complex).

我喜歡關(guān)于量子霸權(quán)的工作。 我真的喜歡。 這對我們這個行業(yè)有好處。 但這是在一個蠻力系統(tǒng)上人造的問題，那里的布線是混亂的（或者至少是復(fù)雜的）。

What we’re trying to do with the hot qubits and with the Horse Ridge chip is put us on a path to scaling that will get us to a useful quantum computer that will change your life or mine. We’ll call that quantum practicality.

我們試圖用熱量子比特和馬嶺芯片做的是讓我們走上一條規(guī)?；牡缆?，這將使我們擁有一臺有用的量子計(jì)算機(jī)，這將改變你的生活或我的生活。 我們稱之為量子實(shí)用性。

Spectrum: What do you think you’re going to work on next most intensely?

Spectrum: 你認(rèn)為下一步你迫切要做的是什么？

Clarke: In other words, “What keeps Jim up at night?”

Clarke:換句話說，“是什么讓我晚上不睡覺？”

Compare that to what we do for transistors: We take a 300-millimeter wafer, put it on a probe station, and after 2 hours we have thousands and thousands of data points across the wafer that tells us something about our yield, our uniformity, and our performance.

與我們對晶體管所做的比較：我們拿一個300毫米的晶片，把它放在探測臺上，2小時后，我們關(guān)于晶片有成千上萬個數(shù)據(jù)點(diǎn)，告訴我們一些關(guān)于我們的產(chǎn)量、均勻性和性能的事情。

What this will do is speed up our time-to-information by a factor of up to 10,000. So instead of wire bonding a single sample, putting it in the fridge, taking a week to study it, or even a few days to study it, we’re going to be able to put a 300-millimeter wafer into this unit and over the course of an evening step and scan. So we’re going to get a tremendous increase in throughput. I would say a 100 X improvement. My engineers would say 10,000. I’ll leave that as a challenge for them to impress me beyond the 100.

這將使我們的信息時間比增大1萬倍。 因此，我們不會用電線連接單個樣品、把它放在制冷機(jī)里、花一個星期的時間來研究它、或者幾天的時間來研究它，我們將能夠在這個單元中放置一個300毫米的晶片，并進(jìn)行一晚上的步進(jìn)和掃描過程。 因此，我們將獲得巨大的生產(chǎn)量增長。 我想說100倍的提升。 我的工程師會說10000倍。 我會把它作為一個挑戰(zhàn)留給他們，給我留下超過100的印象。

Here’s the other thing that keeps me up at night. Prior to starting the Intel quantum-computing program, I was in charge of interconnect research in Intel’s Components Research Group. (This is the wiring on chips.) So, I’m a little less concerned with the wiring into and out of the fridge than I am just about the wiring on the chip.

還有一件事讓我晚上睡不著覺。 在啟動英特爾量子計(jì)算項(xiàng)目之前，我負(fù)責(zé)英特爾部件研究組的互連研究。 （這是芯片上的布線。） 所以，我不太關(guān)心制冷機(jī)里外的連線，而主要關(guān)心芯片上的電線。

I’ll give an example: An Intel server chip has probably north of 10 billion transistors on a single chip. Yet the number of wires coming off that chip is a couple of thousand. A quantum computing chip has more wires coming off the chip than there are qubits. This was certainly the case for the Google [quantum supremacy] work last year. This was certainly the case for the Tangle Lake chip that Intel manufactured in 2018, and it’s the case with our spin qubit chips we make now.

我將舉一個例子：英特爾服務(wù)器芯片可能在單個芯片上有100億個晶體管。 然而，從芯片上連出的電線只有幾千根。 量子計(jì)算芯片連出的導(dǎo)線比量子比特多。 去年谷歌(Google)的“量子霸權(quán)”(quantum superior)工作顯然就是如此。 英特爾在2018年制造的Tangle Lake芯片就是這樣，我們現(xiàn)在制造的自旋量子比特芯片也是這樣。

So we’ve got to find a way to make the interconnects more elegant. We can’t have more wires coming off the chip than we have devices on the chip. It’s ineffective.

因此，我們必須找到一種方法，使互連更加簡潔。 我們不能有比芯片上的設(shè)備更多的電線從芯片上連出。 它是低效率的。

This is something the conventional computing community discovered in the late 1960s with Rent’s Rule [which empirically relates the number of interconnects coming out of a block of logic circuitry to the number of gates in the block]. Last year we published a paper with Technical University Delft on the quantum equivalent of Rent’s Rule. And it talks about, amongst other things the Horse Ridge control chip, the hot qubits, and multiplexing.

這是20世紀(jì)60年代末傳統(tǒng)計(jì)算界在Rent規(guī)則中發(fā)現(xiàn)的某種東西(Rent規(guī)則將邏輯電路塊連出的互連數(shù)與塊中的門數(shù)經(jīng)驗(yàn)性地聯(lián)系起來]。 去年，我們與代爾夫特工業(yè)大學(xué)發(fā)表了一篇關(guān)于Rent規(guī)則的量子等價的論文。 它討論了馬嶺控制芯片、熱量子比特和多路復(fù)用等問題。

Spectrum: Doesn’t Horse Ridge do multiplexing?

Spectrum: 馬嶺控制芯片不能做多路復(fù)用嗎？

Clarke: It has multiplexing. The second generation will have a little bit more. The form factor of the wires [in the new generation] is much smaller, because we can put it in closer proximity to the [quantum] chip.

Clarke:它有多路復(fù)用。 第二代會多一點(diǎn)。 電線的構(gòu)造倍數(shù)[在新一代]要小得多，因?yàn)槲覀兛梢园阉旁诟咏黐量子]芯片的地方。

Spectrum: What’s that going to require?

Spectrum: 那需要什么才能做到？

Clarke: It’s going to require a few things. It’s going to require improvements in the operating temperature of the control chip. It’s probably going to require some novel implementations of the packaging so there isn’t a lot of thermal cross talk between the two chips. It’s probably going to require even greater cooling capacity from the dilution refrigerator. And it’s probably going to require some qubit topology that facilitates multiplexing.

Clarke: 這需要一些東西。 這將需要改進(jìn)控制芯片的工作溫度。 它可能需要一些新穎的封裝方法，這樣兩個芯片之間就不會有太多的熱交換。 它可能需要稀釋制冷機(jī)有更大的冷卻能力。 而且它可能需要一些量子比特拓?fù)浯龠M(jìn)復(fù)用。

Spectrum: Given the significant technical challenges you’ve talked about here, how optimistic are you about the future of quantum computing?

Spectrum: 考慮到您在這里談到的重大技術(shù)挑戰(zhàn)，您對量子計(jì)算的未來有多樂觀？