我們找到了一種新的方式來解釋為什么我們對實(shí)在的本質(zhì)達(dá)成共識(shí)。

一個(gè)受進(jìn)化論啟發(fā)的框架解釋了量子模糊性如何產(chǎn)生我們的經(jīng)典世界，它表明即使是不完美的觀察者最終也能就客觀現(xiàn)實(shí)達(dá)成一致。

作者：卡梅拉·帕達(dá)維奇-卡拉漢

2026年1月27日

我們通常能對物體的外觀達(dá)成共識(shí)，但為什么呢？
Martin Bond / Alamy

從量子層面來看，我們的世界似乎本質(zhì)上是模糊的，但我們實(shí)際體驗(yàn)到的卻并非如此。研究人員現(xiàn)在開發(fā)出一種方法，可以測量我們所體驗(yàn)到的客觀現(xiàn)實(shí)從這種模糊狀態(tài)中涌現(xiàn)的速度，這進(jìn)一步證實(shí)了受進(jìn)化原理啟發(fā)的框架能夠解釋客觀實(shí)在的涌現(xiàn)機(jī)制。

在量子領(lǐng)域，每個(gè)物體——例如單個(gè)原子——都存在于一系列可能的狀態(tài)之中，只有在被測量或觀測之后才會(huì)呈現(xiàn)出明確定義的“經(jīng)典”狀態(tài)。但我們觀測到的卻是完全經(jīng)典的物體，它們不存在任何模糊不清的部分，而造成這種現(xiàn)象的機(jī)制長期以來一直困擾著物理學(xué)家。

2000年，新墨西哥州洛斯阿拉莫斯國家實(shí)驗(yàn)室的沃伊切赫·祖雷克提出了“量子達(dá)爾文主義”。他認(rèn)為，類似于自然選擇的過程能夠確保我們所觀察到的物體狀態(tài)，是所有可能狀態(tài)中最“適應(yīng)”的狀態(tài)，因此也是在到達(dá)觀察者的過程中，通過與環(huán)境相互作用而最能自我復(fù)制的狀態(tài)。當(dāng)兩個(gè)只能接觸到物理實(shí)在片段的觀察者對某些客觀事實(shí)達(dá)成一致時(shí)，是因?yàn)樗麄冇^察到的都是這些相同的復(fù)制體之一。

都柏林大學(xué)學(xué)院的史蒂夫·坎貝爾和他的同事們現(xiàn)在已經(jīng)證明，即使不同的觀察者收集有關(guān)物體的信息的方式（即觀察物體的方式）不是最復(fù)雜或最精確的，他們也可能對客觀實(shí)在達(dá)成一致。

“如果一個(gè)觀察者捕捉到某個(gè)片段，他/她可以選擇進(jìn)行任何他/她想做的測量。我也可以捕捉到另一個(gè)片段，我也可以選擇進(jìn)行任何我想做的測量。那么，經(jīng)典客觀性是如何產(chǎn)生的呢？這就是……”“我們出發(fā)的地方，”他說。

研究人員將客觀性涌現(xiàn)的問題重新定義為量子傳感中的一個(gè)問題。例如，如果待測的客觀事實(shí)是物體發(fā)光的頻率，那么觀察者必須獲得關(guān)于該頻率的精確信息，類似于配備光傳感器的計(jì)算機(jī)的工作方式。在理想情況下，這種裝置可以進(jìn)行超精確的測量，并迅速得出關(guān)于光頻率的明確結(jié)論——這種情況可以用一個(gè)名為“量子費(fèi)舍爾信息”（QFI）的數(shù)學(xué)公式來量化。在這項(xiàng)新研究中，研究人員紐約州羅切斯特大學(xué)的團(tuán)隊(duì)成員加布里埃爾·蘭迪表示，他們以 QFI 為基準(zhǔn)，比較了不同的、不太精確的觀測方案如何得出相同、準(zhǔn)確的結(jié)論。

引人注目的是，該團(tuán)隊(duì)的計(jì)算表明，對于足夠大的物理實(shí)在碎片，即使是進(jìn)行不完美測量的觀察者最終也可以收集到足夠的信息，從而得出與理想的 QFI 標(biāo)準(zhǔn)相同的關(guān)于客觀性的結(jié)論。

蘭迪說：“一種簡單的測量方法實(shí)際上可以和更復(fù)雜的測量方法一樣有效。這是理解古典性出現(xiàn)的一種方式：當(dāng)碎片變得龐大時(shí)?！弊銐蚨嗟臅r(shí)候，觀察者們甚至在簡單的測量上也開始達(dá)成一致?！?通過這種方式，這項(xiàng)研究為我們理解為什么當(dāng)我們觀察宏觀世界時(shí)，我們會(huì)對其物理屬性（例如一杯咖啡的顏色）達(dá)成一致提供了又一步。

“這項(xiàng)研究表明，完美、理想的測量并非必要，”阿根廷布宜諾斯艾利斯大學(xué)的迭戈·維斯尼亞奇（Diego Wisniacki）說道。他表示，量子信息不穩(wěn)定性（QFI）是量子信息理論的基石，但此前從未被引入量子達(dá)爾文主義，因此它可以將這個(gè)仍處于理論階段的量子框架與成熟的實(shí)驗(yàn)（例如量子器件中的實(shí)驗(yàn)）聯(lián)系起來。利用光基或超導(dǎo)量子比特。

“這是我們理解量子達(dá)爾文主義的又一塊‘磚’，”意大利巴勒莫大學(xué)的G·馬西莫·帕爾馬說?！岸?，這種研究方法更接近于實(shí)驗(yàn)學(xué)家對實(shí)驗(yàn)室實(shí)際觀察結(jié)果的描述。”

他說，研究人員在研究中使用的模型非常簡單，因此，雖然他們的方法可能為新的實(shí)驗(yàn)打開大門，但還需要對更復(fù)雜的系統(tǒng)進(jìn)行計(jì)算，才能使量子達(dá)爾文主義建立在更堅(jiān)實(shí)的基礎(chǔ)之上?！叭绻覀兡軌虺浆F(xiàn)有模型，那將是一項(xiàng)真正的重大突破?！迸翣栺R說：“簡單的玩具模型。”

蘭迪表示，研究人員已經(jīng)對將他們的理論研究轉(zhuǎn)化為實(shí)驗(yàn)很感興趣——例如，使用由囚禁離子制成的量子比特，他們可以觀察客觀性出現(xiàn)的時(shí)間尺度與已知這些量子比特保持其量子性的特定時(shí)間相比如何。

期刊參考文獻(xiàn)：
《物理評論A》DOI：10.1103/hn78-7xx3
主題：
量子物理學(xué)

計(jì)量學(xué)方法論視角下的古典客觀性

安東尼·基利、戴安娜·A·奇澤姆、阿克拉姆·圖伊爾、塞巴斯蒂安·德夫納、加布里埃爾·蘭迪和史蒂夫·坎貝爾

《物理評論A》—— 2026年1月14日接收

DOI：https://doi.org/10.1103/hn78-7xx3

導(dǎo)出引用

摘要

我們提出了一種精確刻畫經(jīng)典性出現(xiàn)過程的方法，該方法結(jié)合了量子達(dá)爾文主義的形式體系和量子計(jì)量學(xué)的工具。我們證明，量子費(fèi)舍爾信息為評估經(jīng)典客觀性涌現(xiàn)的速率提供了一個(gè)有用的度量。此外，我們的形式體系允許我們探究測量方法的選擇如何影響觀察者確定系統(tǒng)狀態(tài)的精度。對于自旋星模型的典型例子，我們證明了最優(yōu)測量會(huì)導(dǎo)致經(jīng)典性以指數(shù)級速率涌現(xiàn)。雖然其他測量必然會(huì)導(dǎo)致較慢的涌現(xiàn)速度，但我們的重要發(fā)現(xiàn)是，次優(yōu)測量仍然可以達(dá)到克拉默-拉奧界限。通過將涌現(xiàn)的經(jīng)典性重新表述為信息獲取協(xié)議，我們的框架為量子達(dá)爾文主義提供了一個(gè)精確的操作描述。

• ACCEPTED PAPER

Anthony Kiely, Diana A. Chisholm, Akram Touil, Sebastian Deffner, Gabriel Landi, and Steve Campbell

Phys. Rev. A -Accepted14 January, 2026

DOI: https://doi.org/10.1103/hn78-7xx3

Export Citation

Abstract

We present a precise characterization of the onset of classicality that combines the formalism of quantum Darwinism with the tools from quantum metrology. We show that the quantum Fisher information provides a useful metric for assessing the rate at which classical objectivity emerges. Furthermore, our formalism allows us to explore how the choice of measurement impacts the precision with which an observer can determine the state of the system. For a paradigmatic example of the spin-star model, we demonstrate that optimal measurements lead to the emergence of classicality at an exponential rate. Although other measurements necessarily lead to slower emergence, we importantly show that suboptimal measurements can still saturate the Cramér-Rao bound. By recasting emergent classicality as an information acquisition protocol, our framework provides a precise operational description of quantum Darwinism.

We have a new way to explain why we agree on the nature of reality

An evolution-inspired framework for how quantum fuzziness gives rise to our classical world shows that even imperfect observers can eventually agree on an objective reality

By Karmela Padavic-Callaghan

27 January 2026

We can usually agree what objects look like, but why?

Martin Bond / Alamy

Our world seems to be fundamentally fuzzy at the quantum level, yet we do not experience it that way. Researchers have now developed a recipe for measuring how quickly the objective reality that we do experience emerges from this fuzziness, strengthening the case that a framework inspired by evolutionary principles can explain why it emerges at all.

In the quantum realm, each object – such as a single atom – exists in a cloud of possible states and assumes a well-defined, or “classical”, state only after being measured or observed. But we observe strictly classical objects free of existentially fuzzy parts, and the mechanism that makes this so has long puzzled physicists.

In 2000, Wojciech Zurek at Los Alamos National Laboratory in New Mexico proposed “quantum Darwinism”, where a process similar to natural selection would ensure that the states of objects that we see are those that are most “fit” among all of the many states that could exist, and therefore best at replicating themselves through their interactions with the environment on their way to an observer. When two observers that only have access to fragments of physical reality agree on something objective about it, it is because they are both observing one of these identical copies.

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Steve Campbell at University College Dublin and his colleagues have now proved that different observers are likely to agree on an objective reality even if the way they gather information about an object – the way they observe it – is not the most sophisticated or optimally precise.

“If one observer captures some fragment, they can choose to do whatever measurement they want. I can capture another fragment, and I can choose to do whatever measurement that I want. So how is it that classical objectivity arises? That’s where we started,” he says.

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The researchers recast the problem of objectivity’s emergence as a problem in quantum sensing. If the objective fact at hand is, for example, the frequency at which an object shines light, then the observers must obtain accurate information about that frequency, in a similar way to how a computer equipped with a light sensor would. In the best-case scenario, this set-up could capture super-precise measurements and quickly reach a definitive conclusion about light’s frequency – a scenario quantified by a mathematical formula called “quantum Fisher information”, or QFI. In the new work, the researchers used QFI as a benchmark against which they could compare how different, less precise observation schemes reach the same, accurate conclusions, says team member Gabriel Landi at the University of Rochester in New York state.

Strikingly, the team’s calculations showed that for big enough fragments of physical reality, even observers doing imperfect measurements could eventually gather enough information to reach the same conclusions about objectivity as the ideal QFI standard.

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“A silly measurement can actually do as well as a much more sophisticated measurement,” says Landi. “That’s one way of seeing the emergence of classicality: when the fragments become big enough, observers start agreeing even with simple measurements.” In this way, the work offers another step towards understanding why when we observe our macroscopic world, we agree on its physical properties, such as the colour of a cup of coffee.

“The work highlights that perfect, ideal measurements are not required,” says Diego Wisniacki at the University of Buenos Aires in Argentina. He says that QFI is a mainstay of quantum information theory but it hadn’t been introduced into quantum Darwinism before, so it could bridge this still rather theoretical quantum framework with well-established experiments – for example, in quantum devices with light-based or superconducting qubits.

“This is one more ‘brick’ in our understanding of quantum Darwinism,” says G. Massimo Palma at the University of Palermo in Italy. “And is a way [of studying it] which is closer to an experimentalist’s description of what you actually observe in a lab.”

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The model the researchers used in their study is very simple, so while their method may open doors to new experiments, calculations for more complex systems will be needed to put quantum Darwinism on even firmer foundations, he says. “It would be a really great breakthrough if we could go beyond simple toy models,” says Palma.

Landi says the researchers are already interested in turning their theoretical investigations into an experiment – for example, with qubits made from trapped ions, where they could see how the timescale for the emergence of objectivity compares to the specific times during which those qubits are known to keep their quantumness.

Journal reference:

Physical Review A DOI: 10.1103/hn78-7xx3

Topics:

• Quantum Physics