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Photons traveling straight through a cloud of gas appear to exit, on average, before they enter.

As Homer tells us, Odysseus made an epic journey, against the odds, from Troy to his home in Ithaca. He visited many lands, but mostly dwelt with the nymph Calypso on her island.

We can imagine that his wife, Penelope, would have asked him about that particular time. Odysseus might have replied, “It was nothing. In fact, it was less than nothing. Negative five years I dwelt with Calypso. How else could I have arrived home after only ten years? If you don’t believe me, ask her.”

Quantum particles, it turns out, are just as wily as Odysseus, as my colleagues and I have shown in an experiment published in Physical Review Letters. Not only can their arrival time suggest that they dwelt with other particles for a negative amount of time, but if one asks those other particles, they will corroborate the story.

Photons Dwelling With Atoms

Our experiment used photons—quantum particles of light—and the against-the-odds journey they must undertake to pass straight through a cloud of rubidium atoms.

These atoms have a “resonance” with the photons, meaning the energy of the photon can be transferred temporarily to the atoms as an atomic excitation. This allows the photon to “dwell” in the atomic cloud for a time before being released.

For this resonance to be effective, the photon must have a well-defined energy, matching the amount of energy required to put a rubidium atom into an excited state.

But, by a form of Heisenberg’s famous uncertainty principle, if the energy of the photon is well defined then its timing must be uncertain: The pulse of light the photon occupies must have a long duration. This means we can’t know exactly when the photon enters the cloud, but we can know on average when it enters.

If a photon like this is fired into the cloud, the most likely outcome is that its energy will be transferred to the atoms and then re-emitted as a photon traveling in a random direction. In such cases, the photon is scattered and fails to arrive at its Ithaca.

Photon Arrival Times

But if the photon does make it straight through, a strange thing happens. Based on the average time when the photon enters the cloud, one can calculate the expected average time it would arrive at the far side of the cloud, assuming it travels at the speed of light (as photons usually do).

What one finds is that the photon actually arrives far earlier than that. In fact, it arrives so early it appears to have spent a negative amount of time inside the cloud—to exit, on average, before it enters.

This effect has been known for decades and was observed in a 1993 experiment. But physicists had mostly decided not to take this negative time seriously.

That’s because it can be explained by saying that only the very front of the long-duration pulse makes it straight through the atomic cloud, while the rest is scattered. This leads to a successful (non-scattered) photon arriving earlier than would be naively expected.

Asking the Atoms

However, Aephraim Steinberg, one of the authors of that 1993 paper, was not so quick to accept this dismissal of the negative time as an artifact. In his laboratory at the University of Toronto, he wanted to find out what happened if one queried the rubidium atoms in the cloud to find out how long the photon had spent dwelling among them as an excitation. After an initial experiment with inconclusive results, he asked me, as a quantum theorist, for help in working out what to expect.

When we talk of querying the atoms, what this means in practice is continuously making a measurement on the atoms while the photon is passing through the cloud to probe whether the photon’s energy is currently dwelling there. But there is a subtlety here: Measurements in quantum physics inevitably disturb the system being measured.

If we were to make a precise measurement of whether the photon is dwelling in the atoms, at each instant of time, we would prevent the atoms from interacting with the photon. It is as if, merely by watching Calypso closely, we would stop her getting her hands on Odysseus (or vice versa). This is the well-known quantum Zeno effect, which would destroy the very phenomenon we want to study.

Our Experiment

The solution is to make, instead, a very imprecise (but still very accurately calibrated) measurement. That is the price paid to keep the disturbance negligible. Specifically, we fired a weak laser beam—unrelated to the single photon pulse—through the cloud of atoms, and measured small changes in the phase of the beam’s light to probe whether the atoms were excited.

Any single run of the experiment gives only a very rough indication of whether the photon dwelt in the atoms, but averaging millions of runs yields an accurate dwell time.

Amazingly, the result of this weak measurement of dwell time, when the photon goes straight through the cloud, exactly equals the negative time suggested by the photons’ average arrival time. Prior to our work, no-one suspected that these two times, measured in entirely different ways, would be equal.

Crucially, the negative value of the weakly measured dwell time cannot be explained by imagining that only the front of the photon’s pulse gets through, unlike the time inferred from the arrival time.

So what does this all mean? Is a time machine just around the corner?

Sadly, no. Our experiment is fully explained by standard physics.

But it does show that negative dwell time is not an artifact. However paradoxical it may seem, it has a directly measurable effect on the atomic cloud that the photon traverses. And it reminds us that there are still lands to discover on the odyssey that is quantum research.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The post Physicists Have Measured ‘Negative Time’ in the Lab appeared first on SingularityHub.

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A zero-day exploit circulating online allows people with physical access to a Windows 11 system to bypass default BitLocker protections and gain complete access to an encrypted drive within seconds.

The exploit, named YellowKey, was published earlier this week by a researcher who goes by the alias Nightmare-Eclipse. It reliably bypasses default Windows 11 deployments of BitLocker, the full-volume encryption protection Microsoft provides to make disk contents off-limits to anyone without the decryption key, which is stored in a secured piece of hardware known as a trusted platform module (TPM). BitLocker is a mandatory protection for many organizations, including those that contract with governments.

When one disk volume manipulates another

The core of the YellowKey exploit is a custom-made FsTx folder. Online documentation of this folder is hard to find. As explained later, the directory associated with the file fstx.dll appears to involve what Microsoft calls the transactional NTFS, which allows developers to have “transactional atomicity" for file operations in transactions with a single file, multiple files, or ones that span multiple sources.

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Cisco has released updates to address a maximum-severity authentication bypass flaw in Catalyst SD-WAN Controller that it said has been exploited in limited attacks. The vulnerability, tracked as CVE-2026-20182, carries a CVSS score of 10.0. "A vulnerability in the peering authentication in Cisco Catalyst SD-WAN Controller, formerly SD-WAN vSmart, and Cisco Catalyst SD-WAN Manager, formerly

Cisco has released updates to address a maximum-severity authentication bypass flaw in Catalyst SD-WAN Controller that it said has been exploited in limited attacks. The vulnerability, tracked as CVE-2026-20182, carries a CVSS score of 10.0. "A vulnerability in the peering authentication in Cisco Catalyst SD-WAN Controller, formerly SD-WAN vSmart, and Cisco Catalyst SD-WAN Manager, formerly Ravie Lakshmananhttp://www.blogger.com/profile/[email protected]

Cybersecurity researchers are sounding the alarm about what has been described as "malicious activity" in newly published versions of node-ipc. According to Socket and StepSecurity, three different versions of the npm package have been confirmed as malicious - [email protected] [email protected] [email protected] "Early analysis indicates that [email protected], [email protected], and [email protected]

Cybersecurity researchers are sounding the alarm about what has been described as "malicious activity" in newly published versions of node-ipc. According to Socket and StepSecurity, three different versions of the npm package have been confirmed as malicious - [email protected] [email protected] [email protected] "Early analysis indicates that [email protected], [email protected], and [email protected] Ravie Lakshmananhttp://www.blogger.com/profile/[email protected]

Following a quarter in which his company delivered record revenue, Cisco CEO Chuck Robbins announced that the company's latest round of layoffs begins today.

In a blog post yesterday, Robbins was quick to boast that Cisco’s fiscal Q3 2026 earnings saw revenue increase 12 percent year-over-year to $15.8 billion. He told employees that he and the rest of Cisco’s executive leadership team “could not be prouder of the growth you have all delivered for Cisco.”

But that pride could apparently not save the company’s successful employees from unemployment.

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K2 je projekt na zrychlení a zkvalitnění Windows. • Prioritou pro Microsoft je zlepšení výkonu. • Low Latency Profile zrychlí spuštění aplikací a nabídek.

Do výběru nejlepších sci-fi filmů jsme zvolil tituly, které představují základ žánru a které by měl vidět asi každý. Nevyhýbali jsme se ale ani novým filmům. Vybrali jsme to nejlepší z každé podkategorie, kterých je ve sci-fi více než dost.

Everything is still on fire. This week feels dumb in the worst way — bad links, weak checks, fake help desks, shady forum posts, and people turning supply chain attacks into some cursed little game for clout and cash. Half of it feels new. Half of it feels like crap we should have fixed years ago. The mess keeps getting louder: users get tricked, boxes get popped, tools meant for normal work

Everything is still on fire. This week feels dumb in the worst way — bad links, weak checks, fake help desks, shady forum posts, and people turning supply chain attacks into some cursed little game for clout and cash. Half of it feels new. Half of it feels like crap we should have fixed years ago. The mess keeps getting louder: users get tricked, boxes get popped, tools meant for normal work Ravie Lakshmananhttp://www.blogger.com/profile/[email protected]

Apple has a design for AI life. It hopes to build on the outstanding hardware performance its systems already provide to create a fantastic environment in which AI developers can thrive. If this plan sounds familiar it’s because it’s all about the App Store, and while it’s easy to expect Apple’s revenue share to change, the plan still makes the company the custodian of the AI age.

The way it should work is if app developers see that one way to bring their AI services to billions of iPhones, iPad, and Mac users is to make AI agents available via Apple’s own portals. These will likely be via App Intents, enabling Siri to execute actions inside their apps without actively opening them. 

The Information reports some developers are resistant to joining the initiative, in part because they want to avoid paying any fees. All the same, consider the moment, consider the meaning, and I think the significance is that Apple has at last got its act together with AI.

Ecosystem, services, store

Apple is going to bet that the advantages its existing store provides will give customers the faith and trust to access AI apps there rather than somewhere else. The company hasn’t announced its plan yet, though there have been hints. Just look at how Apple is laying things out with these moves (both announced and speculated about). It’s:

• Working with Google to build out Apple Intelligence.
• Working with third parties to support AI services as apps with which to replace or supplement Siri.
• Maintaining investment in better hardware to run AI — you can quite happily run some models natively on an iPad. 
• Equipping systems with powerful tools such as Unified Memory and the Neural Engine.
• Rolling out Apple Private Cloud Computer to provide an infrastructure to support private AI in the cloud.
• Pulling these elements together to form an ecosystem.

Like a jigsaw, the pieces fit together to provide a fantastic base from which Apple can distribute increasingly powerful AI APIs developers can use to create amazing AI experiences. I spoke with the smart people at the OmniGroup just last year who explained how they already use Apple Intelligence APIs (aka Foundation Models) to add powerful AI features to apps. 

That was just the first lap; the second comes at WWDC 2026; and the third and subsequent races take place over the next 12 to 24 months as Apple implements the elements it’s put in place across its ecosystem. 

Making money, one token at a time

The prize? For Apple, it’s about maintaining its own relevance within the AI age while carving out some way to generate revenue as its hardware ecosystem runs AI agents and services. The company will continue to develop and build out Apple Intelligence as a peer player in the competitive AI market. But, as most now agree, it is also focused on ensuring its platforms are the best systems on which to run AI.

Apple’s attempt to build a profitable, secure, and capable way to run AI — supported by customer-focused security and privacy standards— seems like an answer to some of the emerging challenges around AI deployment. Speak to almost anyone in IT right now and you’ll come across stories of corporate data leaks that may fall foul of data regulation. That’s before you even consider the manner in which AI ownership consolidates power over the intellectual future of humanity into such a small number of hands it almost makes media ownership seem democratic.

Getting the band together

With so much at stake, not just for Apple, it feels as if the company has found some of the answers that could enable a less frightening AI future. It has a chance to own the hardware ecosystem while curating the AI services environment for the benefit of its customers — and producing its own trusted systems for casual AI usage.

We’ll find out more in a few weeks.

You can follow me on social media! Join me on BlueSky,  LinkedIn, and Mastodon.

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