In a small entrance on Blegdamsvej in Østerbro, Jan Westenkær Thomsen, head of the Niels Bohr Institute, knocks on the door where modern civilization was born. Nobody answers, and he pulls the handle.

15 minutes earlier, at his office in an adjacent building, he had tried to explain the era-defining events that had happened behind the white door 90 years ago:

“This is where it started! A completely new type of physics. A new kind of worldview, which meant that we could understand the microscopic world much better. We could reasonably rely on it and make precise predictions, so precise, that it led to the transistor radio, to your laptop, to modern electronics. That’s what we call the first quantum revolution. It started just here!”

The room is sparsely decorated. White walls, six white benches with space for 60 people and a large blackboard built into one wall. It has looked this way since 1921, except for the blackboard, which was modified in 1934.

Auditorium A is still being used for lectures and education (as long as it lasts) but right now it is empty. There is not much hanging on the walls. A few photographs. One of them was taken in 1930, up from the podium. 19 men and a single woman are sitting on the benches. They are Niels Bohr and his disciples. Four of them are future Nobel laureates in physics. Three are future recipients of the Max Planck medal. The man who will become known as “the father of the hydrogen bomb,” is sitting in the middle row. So is Danish poet and inventor Piet Hein, who began, and never completed his physics studies at the Bohr Institute. They look stiff and formal, except Hein, who – anti-authoritarian as he was – is not wearing a tie.

But the image of the serious researchers is deceiving, says Westenkær Thomsen.

“I like taking people over to auditorium A and showing them where Niels Bohr and his allies worked and argued. And I say argued, because there were strong opinions which clashed. There were intense discussions about molecules, atoms, quantum mechanical interpretations of systems. When I take people over here, I say “This is the birthplace of modern civilization. Right here. In these rooms. That’s the soul!”

It is not only the past and the legacy of Niels Bohr, which enthuses him. At the moment, several of his colleagues are on the verge of a scientific breakthrough so huge, he doesn’t hesitate to call it “the second quantum revolution.”

Amidst it all, in the enthusiasm about the past and future prospects, Thomsen will also lead a project which has prompted major concern among employees. According to one of them, it threatens the sheer existence of the institute.

The Niels Bohr Institute, Denmark’s most internationally-renowned institute, is to be relocated. A giant building of glass and concrete, plagued by scandal, is waiting just one kilometre away on Jagtvej – when it (hopefully) will be ready for the move in 2019. Westenkær Thomsen says himself that part of the institute’s spirit lies in the old buildings along Blegdamsvej. How will he ensure that the spirit can be relocated?

In the adjacent building, all the way below the ceiling, three experts in the institute’s history are helping to define the nature of the spirit that must be preserved in the move.

“This image tells the story of how international the place was from day one,” says Christian Joas, German historian of science and recently-appointed head of the Niels Bohr Archive, referring to a grainy staff image from the institute’s opening in 1921: among the eight employees (including Bohr himself), six nationalities are represented.

We’re sitting at Christian’s desk together with his predecessor Finn Aaserud and archivist emeritus Felicity Pors to escape the loud noises made by the workers outside, who are renovating the windows on the protected building.

It was Bohr himself, who built it. Not with his own hands, but something close to it.

He graduated from the University of Copenhagen in 1911, and when he was employed at the same institution as a professor five years later, it was with the clear ambition to create an institute which could offer proper conditions for physics at UCPH. In the meantime, Bohr had achieved international fame with his atomic model. With this recognition, he was able to obtain the money, grounds and building permits necessary so that The University of Copenhagen’s Institute for Theoretical physics could open on Blegdamsvej in 1921.

“Bohr was a special person. He lived a kind of double life. When he was with the students, he was completely dedicated to physics. But at the same time, he was in a position to raise funds for the institute – and he completely separated the two tasks,” says Aaserud, adding that the fundraising was not necessarily the part of Bohr’s legacy that researchers at the institute identified with over time: “When I came here in 89’ and suggested that Bohr was interested in finances and such matters of the material world, I was considered by some as almost a communist.”

There is, however, large consensus over other aspects of Bohr’s spirit. For example, his ability to attract international talent.

From 1921 to 1961, 444 researchers from 35 countries spent one month or more at the Bohrs Institute. According to Joas, it had a special meaning that the Danes opened the doors to German research talents who nobody would collaborate with in the UK and France in the years following the First World War. This pattern repeated itself during the Cold War, where Bohr held the doors open for Russian researchers, and his institute became one of the few places in the world where physicists from both sides of the Iron Curtain met and exchanged theories.

When the international researchers came to Copenhagen, they were confronted with another thing which today is considered an important part of Bohr’s legacy and spirit:

“There are reports that German researchers were shocked by the informal atmosphere in the 1920s,” says Aaserud. “They were not used to the fact that you could open the door to an auditorium and see a Russian scientist lying on his back on the table with the big professor leaning over him in the midst of a heated discussion.”

This informality was also expressed by Bohr’s fondness for the playfulness. In the annual Copenhagen Conferences (Københavnerkonferencer), held since 1929, the audience played on a toy trumpet if they liked what was said and fired a shot from a miniature canon if a theory had holes in it. The young physicists performed sketches and produced the Journal of Jocular Physics with humourous descriptions of life and research at the institute. Bohr generally did not impose many limits, says Aaserud, except when the students played table tennis with his books.

There is also a third element that many at the institute name when asked about Bohr’s spirit: stubbornness. A beloved anecdote testifying to this harks back to 1926, when Bohr was visited by the physicist Erwin Schrödinger, who did not buy the interpretation of quantum mechanics put forward by Bohr and his protégé Werner Heisenberg.

“During a visit Schrödinger became sick, but even though he had a high fever, Bohr remained by his bedside and insisted on further discussion. That must have been an intense experience,” says Joas.

Just as renowned were Bohr’s discussions with Einstein on the same subject as the Solvay conferences in Brussels. Nor did Einstein accept Bohr’s interpretation of quantum mechanics.

Aaserud knows another story about Bohr’s persistence, and Einstein’s, for that matter:

“Einstein visited Bohr before the institute was built. The story goes that Bohr picked him up at the central train station, after which they took a tram – and ended up riding back and forth between the final stations, because they were so caught up in their discussion that they forgot to get off.”

On the ground floor of the professor villa, time stands still. Thomsen has opened the door to Bohr’s study, which stands exactly as it was in Bohr’s time. On the walls, there are fading images of physics professors and photographs of the Institute’s employees, one for each year.

“Sometimes we use the room, when one of the major funds signs a large grant agreement,” says Westenkær Thomsen.

In the first years, Bohr’s room had been part of the family’s home, until they moved into the honorary residence at Carlsberg in Valby.

Before the institute was built, and before Bohr was married, he asked his fiancée in a letter whether she would act as a mother to his students if he managed to establish his institute. She took up the task. Researchers at the institute became part of the family when they arrived. In pictures dating back to the early 30’s, you can see Bohr’s children playing with Lev Landau, George Gamow and Edward Teller – or Uncle Landau, Uncle Gamow, and Uncle Teller, as they were called by the children.

When the young American Ben Mottelson arrived in Copenhagen in 1950 with his wife and their newborn son, the Bohr family took him in with open arms.

The son, Malcolm, says one of his earliest memories is the Christmas tree celebrations in Bohr’s home at Carlsberg.

And it was not only the employees who were treated as a part of the extended Bohr family.

“Margrethe Bohr had the idea to invite young students to afternoon tea to get to know them,” says Thomsen.

“This is something which lives on today. The sense of openness. There is a kind of family essence to the institute.”

On the facade of the original institute building, Auditorium A, several letters are attached. Originally, they spelled “The University Institute for Theoretical Physics,” but in 1965 – three years after Bohr’s death – the institute changed its name to what it had always been called: Niels Bohr Institute.

10 years later, Mottelson and Aage Bohr, Niels’ son, received the Noble Prize in physics for their collective model of the nucleus.

Joas says that the decades after Bohr’s death – in particular from the 1980’s and forward – are referred to by some as a downturn, even though the institute continued to be internationally recognized and attracted researchers from abroad. According to Joas, there are several factors which could have contributed to a sense of decline:

One factor was that the epicentre of physics in Europe moved to Geneva which is the home of CERN, Europe’s laboratory for nuclear and particle physics, which Bohr himself was part of establishing in the 1950s –  where advanced particle accelerators made it possible to research the smallest particles in the universe.

A second factor was an institute merger at the University of Copenhagen, which in 1993 added solid state physics, geophysics and astronomy under the umbrella of the Niels Bohr Institute, which according to some researchers risked diluting the identity of the institute.

A third factor was a more general change in the status of science, which according to Joas occurred concurrently:

“If you look at it from a bigger perspective, physics no longer plays the same major role for political decision makers as it did in previous decades. According to them, it is health science that is on the way forward,” he says.

If you believe Thomsen, researchers at the Niels Bohr Institute are on the verge of a breakthrough which could change this. One kilometre away, in building 3 in Universitetsparken, lies the Niels Bohr Institute’s Center for Quantum Devices. Here, Microsoft has moved in with the highly-profiled professor Charles Marcus, in the hope of being able to use his research into Q-bits (quantum bits) to develop the world’s first scalable quantum computer within a few years.

Thomsen tries to explain the research and perspectives in layman’s terms:

“Normal bits could be either 0 or 1. A transistor opens and closes for an electric current. The laptop you write on consists of a lot of doors that open and close for currents. But in quantum mechanics, bits can be both 0s and 1s at the same time – in different weights. This means that completely new possibilities open up. The volume of information which can be saved grows exponentially. 300 Q-bits will be able to accommodate more bits than there are atoms in the universe.

Marcus is not the only one attracting large funds to quantum research. In the cellar under Blegdamsvej 17, another research team led by Peter Lodahl has taken major steps in quantum photonics which can pave the way for solving complex computing challenges which today’s supercomputers cannot.

When the researches succeed – Westenkær Thomsen says “when” not “if” – the second quantum revolution will become a reality.

“This has an international focus. The larger funds are interested. The larger universities are working with it. There is a huge energy around the field. Also because there is technological power in it. Who comes forth with the ideas first?”

At the entrance to Bohr’s villa on Blegdamsvej, there is a large bronze relief made by the artist Rikke Raben, which show’s the institute’s four, home-grown Nobel Prize winners:  Niels Bohr, George de Hevesy, Aage Bohr and Ben Mottelson.

Niels Bohr Institute has ordered two copies of the relief. The second will hang in the new Niels Bohr building on Jagtvej and greet the Institute’s staff and students when they move. If they move.

This is a headache for Thomsen. Amidst the exictement about the coming of the second quantum revolution, he is overseeing the institute’s relocation from the historic buildings on Blegdamsvej. The physical and chemical courses will be moved to the large Niels Bohr building on Jagtvej, which has been struck by serious building errors and delayed by at least two years. The bill for the building has also increased from 1.6 billion kroner to nearly 3 billion kroner.

Thomsen’s employees at the Dark Cosmology Center and Center for Ice and Climate, which form part of the Rockefeller Complex at Copenhagen’s hospital Righospitalet, have already been forced to move out of their current premises and will be temporarily rehoused. He does not know where the university will find space for them. And they will have to move again when the building on Jagtvej is ready. The researchers risk putting their research on hold for at least six months.

“They are sad about it, to put it mildly,” says Westenkær Thomsen.

And even if everything goes well, and the entire institute is locked into place on Jagtvej, he still faces a challenge. He has spoken with several employees who are concerned about the move:

“The research culture on Blegdamsvej, the good conditions we have … will we get the same conditions? Everyone is anxious about it. And I understand that. Especially with my research background. But is it valid? I cannot answer that. Time will tell. I do not know.”

One of his team members, professor Kim Sneppen, has opposed relocation since the first plans for a new building were drawn up in 2006.

“It is quite clear that the consideration has not been ongoing in connection with the new building. This is almost a parody,” he says.

“The building has less space – and more glass, in every way. Common areas will be located in a large, empty, 4-story hall in the middle, so that there can be a ‘universal synergy’ between everyone. It simply doesn’t work like that. A train station is not the right meeting place.”

According to Sneppen, Bohr – who notoriously became involved in all the building projects for the institute – put great thought into the buildings on Blegdamsvej.

“He tried to make sure that there were plenty of small offices and areas where you could meet. There were both places, you could meet privately and open spaces perfect for discussion. The small crooks and strange passages that we have here, will disappear in the new building. It will be hard to keep the same atmosphere.”

11 years ago, Sneppen wrote in a column that the move would “with one stroke, eliminate the most famous institute in Danish research.”

“I still believe that. We will end up with a huge Niels Bohr science park. The Institute will disappear – it will become just a name.”

Jan Thomsen sees the future more brightly.

“A spirit does not only live in the buildings. It also lives in the working culture and the access to research, which students, professors, lecturers and the technical and administrative personale have. And if we get the conditions we were promised, we will be happy. Truly happy. We will be closer to the chemists and the mathematicians. This is a huge advantage. Plus, we’ll also get completely new laboratory facilities.”

At Bohr’s villa, the workers are carrying on with the windows.

When the Institute moves, the original building with Auditorium A, the villa with Bohr’s office and the building which currently houses Niels Bohr International Academy, will remain standing as they are. The Niels Bohr Archive expects to remain on Blegdamsvej. The Institute’s other buildings, which have proliferated over the years, will return to the state, which can opt to rent them out or sell them.

Joas stands at the back entrance to the villa and bids farewell to the Uniavisen reporters when the back door opens. Out comes a short, old man with with a thick physics book under his arm. This is Ben Mottelson, who today is 92 years old and the only living Nobel Prize winner at the University of Copenhagen.

Joas greets him.

“We have just seen a picture of you from the 1950s, where you are standing and drinking beer from a jug,« he says.

Mottelson smiles. His memory is not quite what it has been, but he still visits his corner office near the institute’s library three-four times per week. We have also seen images of him playing soccer in Fælledparken on the other side of the buildings, of young postdocs pushing around Niels Bohr’s children in soapbox cars on Blegdamsvej, of Bohr himself, when he returned to the institute – on his bike – after being exiled during the Second World War.

In the Institute’s garden, a stone’s throw away, there are several old magnolia trees. Rikke Raben, the artist behind the reliefs, went for a walk five-six years ago and noticed a bud with seeds in the ground, which she gave to the Dean John Renner Hansen, who made sure that the seeds were planted outside the new Niels Bohr Building, so a small part of the institute on Blegdamsvej can live on after the move.

If the Niels Bohr building is ready. If so, there is a part of Bohr’s spirit which already lives on in the new premises, the archive’s staff point out. And as good historians, they also have a literary reference prepared, lifted from Peter Robertson’s book The Early Years regarding the birth of the Niels Bohr Institute:

“With work continuing on the Institute throughout 1920, the plan for the official opening had to be put aside indefinitely. The setbacks that had arisen over the purchase of the site in 1918 and the strikes by the building workers in 1919, as well as a host of other problems in the construction and installation of the building, all combined to delay the completion of the Institute for nearly two years. These setbacks were a continual source of worry and disappointment for Bohr.”

“You can see it as a good sign,” says Aaserud dryly. “Even the delay is consistent with Niel Bohr’s spirit.”